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diff --git a/en_US.ISO8859-1/articles/storage-devices/article.sgml b/en_US.ISO8859-1/articles/storage-devices/article.sgml deleted file mode 100644 index b3778f8ebb..0000000000 --- a/en_US.ISO8859-1/articles/storage-devices/article.sgml +++ /dev/null @@ -1,2627 +0,0 @@ -<!DOCTYPE article PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [ -<!ENTITY % man PUBLIC "-//FreeBSD//ENTITIES DocBook Manual Page Entities//EN"> -%man; -<!ENTITY % authors PUBLIC "-//FreeBSD//ENTITIES DocBook Author Entities//EN"> -%authors; -]> - -<article> - <articleinfo> - <title>Storage Devices</title> - - <authorgroup> - <author> - <firstname>Wilko</firstname> - <surname>Bulte</surname> - - <affiliation> - <address><email>wilko@FreeBSD.org</email></address> - </affiliation> - </author> - </authorgroup> - - <pubdate>$FreeBSD: doc/en_US.ISO8859-1/articles/storage-devices/article.sgml,v 1.1 2001/07/13 22:30:40 murray Exp $</pubdate> - - <abstract> - <para>This article talks about storage devices with FreeBSD.</para> - </abstract> - </articleinfo> - - <sect1 id="esdi"> - <title>Using ESDI hard disks</title> - - <para><emphasis>Copyright © 1995, &a.wilko;. 24 September - 1995.</emphasis></para> - - <para>ESDI is an acronym that means Enhanced Small Device - Interface. It is loosely based on the good old ST506/412 - interface originally devised by Seagate Technology, the makers - of the first affordable 5.25" winchester disk.</para> - - <para>The acronym says Enhanced, and rightly so. In the first - place the speed of the interface is higher, 10 or 15 - Mbits/second instead of the 5 Mbits/second of ST412 interfaced - drives. Secondly some higher level commands are added, making - the ESDI interface somewhat 'smarter' to the operating system - driver writers. It is by no means as smart as SCSI by the way. - ESDI is standardized by ANSI.</para> - - <para>Capacities of the drives are boosted by putting more sectors - on each track. Typical is 35 sectors per track, high capacity - drives I have seen were up to 54 sectors/track.</para> - - <para>Although ESDI has been largely obsoleted by IDE and SCSI - interfaces, the availability of free or cheap surplus drives - makes them ideal for low (or now) budget systems.</para> - - <sect2> - <title>Concepts of ESDI</title> - - <sect3> - <title>Physical connections</title> - - <para>The ESDI interface uses two cables connected to each drive. - One cable is a 34 pin flat cable edge connector that carries the - command and status signals from the controller to the drive and - vice-versa. The command cable is daisy chained between all the - drives. So, it forms a bus onto which all drives are - connected.</para> - - <para>The second cable is a 20 pin flat cable edge connector that - carries the data to and from the drive. This cable is radially - connected, so each drive has its own direct connection to the - controller.</para> - - <para>To the best of my knowledge PC ESDI controllers are limited to - using a maximum of 2 drives per controller. This is compatibility - feature(?) left over from the WD1003 standard that reserves only a - single bit for device addressing.</para> - </sect3> - - <sect3> - <title>Device addressing</title> - - <para>On each command cable a maximum of 7 devices and 1 controller - can be present. To enable the controller to uniquely identify - which drive it addresses, each ESDI device is equipped with - jumpers or switches to select the devices address.</para> - - <para>On PC type controllers the first drive is set to address 0, - the second disk to address 1. <emphasis>Always make - sure</emphasis> you set each disk to an unique address! So, on a - PC with its two drives/controller maximum the first drive is drive - 0, the second is drive 1.</para> - </sect3> - - <sect3> - <title>Termination</title> - - <para>The daisy chained command cable (the 34 pin cable remember?) - needs to be terminated at the last drive on the chain. For this - purpose ESDI drives come with a termination resistor network that - can be removed or disabled by a jumper when it is not used.</para> - - <para>So, one and <emphasis>only</emphasis> one drive, the one at - the farthest end of the command cable has its terminator - installed/enabled. The controller automatically terminates the - other end of the cable. Please note that this implies that the - controller must be at one end of the cable and - <emphasis>not</emphasis> in the middle.</para> - </sect3> - </sect2> - - <sect2> - <title>Using ESDI disks with FreeBSD</title> - - <para>Why is ESDI such a pain to get working in the first - place?</para> - - <para>People who tried ESDI disks with FreeBSD are known to have - developed a profound sense of frustration. A combination of factors - works against you to produce effects that are hard to understand - when you have never seen them before.</para> - - <para>This has also led to the popular legend ESDI and FreeBSD is a - plain NO-GO. The following sections try to list all the pitfalls - and solutions.</para> - - <sect3> - <title>ESDI speed variants</title> - - <para>As briefly mentioned before, ESDI comes in two speed flavors. - The older drives and controllers use a 10 Mbits/second data - transfer rate. Newer stuff uses 15 Mbits/second.</para> - - <para>It is not hard to imagine that 15 Mbits/second drive cause - problems on controllers laid out for 10 Mbits/second. As always, - consult your controller <emphasis>and</emphasis> drive - documentation to see if things match.</para> - </sect3> - - <sect3> - <title>Stay on track</title> - - <para>Mainstream ESDI drives use 34 to 36 sectors per track. Most - (older) controllers cannot handle more than this number of - sectors. Newer, higher capacity, drives use higher numbers of - sectors per track. For instance, I own a 670 MB drive that has 54 - sectors per track.</para> - - <para>In my case, the controller could not handle this number of - sectors. It proved to work well except that it only used 35 - sectors on each track. This meant losing a lot of disk - space.</para> - - <para>Once again, check the documentation of your hardware for more - info. Going out-of-spec like in the example might or might not - work. Give it a try or get another more capable - controller.</para> - </sect3> - - <sect3> - <title>Hard or soft sectoring</title> - - <para>Most ESDI drives allow hard or soft sectoring to be selected - using a jumper. Hard sectoring means that the drive will produce - a sector pulse on the start of each new sector. The controller - uses this pulse to tell when it should start to write or - read.</para> - - <para>Hard sectoring allows a selection of sector size (normally - 256, 512 or 1024 bytes per formatted sector). FreeBSD uses 512 - byte sectors. The number of sectors per track also varies while - still using the same number of bytes per formatted sector. The - number of <emphasis>unformatted</emphasis> bytes per sector - varies, dependent on your controller it needs more or less - overhead bytes to work correctly. Pushing more sectors on a - track of course gives you more usable space, but might give - problems if your controller needs more bytes than the drive - offers.</para> - - <para>In case of soft sectoring, the controller itself determines - where to start/stop reading or writing. For ESDI hard sectoring - is the default (at least on everything I came across). I never - felt the urge to try soft sectoring.</para> - - <para>In general, experiment with sector settings before you install - FreeBSD because you need to re-run the low-level format after each - change.</para> - </sect3> - - <sect3> - <title>Low level formatting</title> - - <para>ESDI drives need to be low level formatted before they are - usable. A reformat is needed whenever you figgle with the number - of sectors/track jumpers or the physical orientation of the drive - (horizontal, vertical). So, first think, then format. The format - time must not be underestimated, for big disks it can take - hours.</para> - - <para>After a low level format, a surface scan is done to find and - flag bad sectors. Most disks have a manufacturer bad block list - listed on a piece of paper or adhesive sticker. In addition, on - most disks the list is also written onto the disk. Please use the - manufacturer's list. It is much easier to remap a defect now than - after FreeBSD is installed.</para> - - <para>Stay away from low-level formatters that mark all sectors of a - track as bad as soon as they find one bad sector. Not only does - this waste space, it also and more importantly causes you grief - with bad144 (see the section on bad144).</para> - </sect3> - - <sect3> - <title>Translations</title> - - <para>Translations, although not exclusively a ESDI-only problem, - might give you real trouble. Translations come in multiple - flavors. Most of them have in common that they attempt to work - around the limitations posed upon disk geometries by the original - IBM PC/AT design (thanks IBM!).</para> - - <para>First of all there is the (in)famous 1024 cylinder limit. For - a system to be able to boot, the stuff (whatever operating system) - must be in the first 1024 cylinders of a disk. Only 10 bits are - available to encode the cylinder number. For the number of - sectors the limit is 64 (0-63). When you combine the 1024 - cylinder limit with the 16 head limit (also a design feature) you - max out at fairly limited disk sizes.</para> - - <para>To work around this problem, the manufacturers of ESDI PC - controllers added a BIOS prom extension on their boards. This - BIOS extension handles disk I/O for booting (and for some - operating systems <emphasis>all</emphasis> disk I/O) by using - translation. For instance, a big drive might be presented to the - system as having 32 heads and 64 sectors/track. The result is - that the number of cylinders is reduced to something below 1024 - and is therefore usable by the system without problems. It is - noteworthy to know that FreeBSD does not use the BIOS after its - kernel has started. More on this later.</para> - - <para>A second reason for translations is the fact that most older - system BIOSes could only handle drives with 17 sectors per track - (the old ST412 standard). Newer system BIOSes usually have a - user-defined drive type (in most cases this is drive type - 47).</para> - - <warning> - <para>Whatever you do to translations after reading this document, - keep in mind that if you have multiple operating systems on the - same disk, all must use the same translation</para> - </warning> - - <para>While on the subject of translations, I have seen one - controller type (but there are probably more like this) offer the - option to logically split a drive in multiple partitions as a BIOS - option. I had select 1 drive == 1 partition because this - controller wrote this info onto the disk. On power-up it read the - info and presented itself to the system based on the info from the - disk.</para> - </sect3> - - <sect3> - <title>Spare sectoring</title> - - <para>Most ESDI controllers offer the possibility to remap bad - sectors. During/after the low-level format of the disk bad - sectors are marked as such, and a replacement sector is put in - place (logically of course) of the bad one.</para> - - <para>In most cases the remapping is done by using N-1 sectors on - each track for actual data storage, and sector N itself is the - spare sector. N is the total number of sectors physically - available on the track. The idea behind this is that the - operating system sees a 'perfect' disk without bad sectors. In - the case of FreeBSD this concept is not usable.</para> - - <para>The problem is that the translation from - <emphasis>bad</emphasis> to <emphasis>good</emphasis> is performed - by the BIOS of the ESDI controller. FreeBSD, being a true 32 bit - operating system, does not use the BIOS after it has been booted. - Instead, it has device drivers that talk directly to the - hardware.</para> - - <para><emphasis>So: don't use spare sectoring, bad block remapping - or whatever it may be called by the controller manufacturer when - you want to use the disk for FreeBSD.</emphasis></para> - </sect3> - - <sect3> - <title>Bad block handling</title> - - <para>The preceding section leaves us with a problem. The - controller's bad block handling is not usable and still FreeBSD's - filesystems assume perfect media without any flaws. To solve this - problem, FreeBSD use the <command>bad144</command> tool. Bad144 - (named after a Digital Equipment standard for bad block handling) - scans a FreeBSD slice for bad blocks. Having found these bad - blocks, it writes a table with the offending block numbers to the - end of the FreeBSD slice.</para> - - <para>When the disk is in operation, the disk accesses are checked - against the table read from the disk. Whenever a block number is - requested that is in the <command>bad144</command> list, a - replacement block (also from the end of the FreeBSD slice) is - used. In this way, the <command>bad144</command> replacement - scheme presents 'perfect' media to the FreeBSD filesystems.</para> - - <para>There are a number of potential pitfalls associated with the - use of <command>bad144</command>. First of all, the slice cannot - have more than 126 bad sectors. If your drive has a high number - of bad sectors, you might need to divide it into multiple FreeBSD - slices each containing less than 126 bad sectors. Stay away from - low-level format programs that mark <emphasis>every</emphasis> - sector of a track as bad when they find a flaw on the track. As - you can imagine, the 126 limit is quickly reached when the - low-level format is done this way.</para> - - <para>Second, if the slice contains the root filesystem, the slice - should be within the 1024 cylinder BIOS limit. During the boot - process the bad144 list is read using the BIOS and this only - succeeds when the list is within the 1024 cylinder limit.</para> - - <note> - <para>The restriction is not that only the root - <emphasis>filesystem</emphasis> must be within the 1024 cylinder - limit, but rather the entire <emphasis>slice</emphasis> that - contains the root filesystem.</para> - </note> - </sect3> - - <sect3> - <title>Kernel configuration</title> - - <para>ESDI disks are handled by the same <literal>wd</literal>driver - as IDE and ST412 MFM disks. The <literal>wd</literal> driver - should work for all WD1003 compatible interfaces.</para> - - <para>Most hardware is jumperable for one of two different I/O - address ranges and IRQ lines. This allows you to have two wd - type controllers in one system.</para> - - <para>When your hardware allows non-standard strappings, you can use - these with FreeBSD as long as you enter the correct info into the - kernel config file. An example from the kernel config file (they - live in <filename>/sys/i386/conf</filename> BTW).</para> - - <programlisting># First WD compatible controller -controller wdc0 at isa? port "IO_WD1" bio irq 14 vector wdintr -disk wd0 at wdc0 drive 0 -disk wd1 at wdc0 drive 1 -# Second WD compatible controller -controller wdc1 at isa? port "IO_WD2" bio irq 15 vector wdintr -disk wd2 at wdc1 drive 0 -disk wd3 at wdc1 drive 1</programlisting> - </sect3> - </sect2> - - <sect2> - <title>Particulars on ESDI hardware</title> - - <sect3> - <title>Adaptec 2320 controllers</title> - - <para>I successfully installed FreeBSD onto a ESDI disk controlled - by a ACB-2320. No other operating system was present on the - disk.</para> - - <para>To do so I low level formatted the disk using - <command>NEFMT.EXE</command> (<command>ftp</command>able from - <hostid role="fqdn">www.adaptec.com</hostid>) and answered NO to - the question whether the disk should be formatted with a spare - sector on each track. The BIOS on the ACD-2320 was disabled. I - used the <literal>free configurable</literal> option in the system - BIOS to allow the BIOS to boot it.</para> - - <para>Before using <command>NEFMT.EXE</command> I tried to format - the disk using the ACB-2320 BIOS built-in formatter. This proved - to be a show stopper, because it did not give me an option to - disable spare sectoring. With spare sectoring enabled the FreeBSD - installation process broke down on the <command>bad144</command> - run.</para> - - <para>Please check carefully which - ACB-232<replaceable>xy</replaceable> variant you have. The - <replaceable>x</replaceable> is either <literal>0</literal> or - <literal>2</literal>, indicating a controller without or with a - floppy controller on board.</para> - - <para>The <literal>y</literal> is more interesting. It can either - be a blank, a <literal>A-8</literal> or a <literal>D</literal>. A - blank indicates a plain 10 Mbits/second controller. An - <literal>A-8</literal> indicates a 15 Mbits/second controller - capable of handling 52 sectors/track. A <literal>D</literal> - means a 15 Mbits/second controller that can also handle drives - with > 36 sectors/track (also 52 ?).</para> - - <para>All variations should be capable of using 1:1 interleaving. - Use 1:1, FreeBSD is fast enough to handle it.</para> - </sect3> - - <sect3> - <title>Western Digital WD1007 controllers</title> - - <para>I successfully installed FreeBSD onto a ESDI disk controlled - by a WD1007 controller. To be precise, it was a WD1007-WA2. - Other variations of the WD1007 do exist.</para> - - <para>To get it to work, I had to disable the sector translation and - the WD1007's onboard BIOS. This implied I could not use the - low-level formatter built into this BIOS. Instead, I grabbed - <command>WDFMT.EXE</command> from <hostid - role="fqdn">www.wdc.com</hostid> Running this formatted my drive - just fine.</para> - </sect3> - - <sect3> - <title>Ultrastor U14F controllers</title> - - <para>According to multiple reports from the net, Ultrastor ESDI - boards work OK with FreeBSD. I lack any further info on - particular settings.</para> - </sect3> - </sect2> - - <sect2 id="esdi-further-reading"> - <title>Further reading</title> - - <para>If you intend to do some serious ESDI hacking, you might want to - have the official standard at hand:</para> - - <para>The latest ANSI X3T10 committee document is: Enhanced Small - Device Interface (ESDI) [X3.170-1990/X3.170a-1991] [X3T10/792D - Rev 11]</para> - - <para>On Usenet the newsgroup <ulink - url="news:comp.periphs">comp.periphs</ulink> is a noteworthy place - to look for more info.</para> - - <para>The World Wide Web (WWW) also proves to be a very handy info - source: For info on Adaptec ESDI controllers see <ulink - url="http://www.adaptec.com/">http://www.adaptec.com/</ulink>. For - info on Western Digital controllers see <ulink - url="http://www.wdc.com/">http://www.wdc.com/</ulink>.</para> - </sect2> - - <sect2> - <title>Thanks to...</title> - - <para>Andrew Gordon for sending me an Adaptec 2320 controller and ESDI - disk for testing.</para> - </sect2> - </sect1> - - <sect1 id="scsi"> - <title>What is SCSI?</title> - - <para><emphasis>Copyright © 1995, &a.wilko;. July 6, - 1996.</emphasis></para> - - <para>SCSI is an acronym for Small Computer Systems Interface. It is an - ANSI standard that has become one of the leading I/O buses in the - computer industry. The foundation of the SCSI standard was laid by - Shugart Associates (the same guys that gave the world the first mini - floppy disks) when they introduced the SASI bus (Shugart Associates - Standard Interface).</para> - - <para>After some time an industry effort was started to come to a more - strict standard allowing devices from different vendors to work - together. This effort was recognized in the ANSI SCSI-1 standard. - The SCSI-1 standard (approximately 1985) is rapidly becoming obsolete. The - current standard is SCSI-2 (see <link - linkend="scsi-further-reading">Further reading</link>), with SCSI-3 - on the drawing boards.</para> - - <para>In addition to a physical interconnection standard, SCSI defines a - logical (command set) standard to which disk devices must adhere. - This standard is called the Common Command Set (CCS) and was developed - more or less in parallel with ANSI SCSI-1. SCSI-2 includes the - (revised) CCS as part of the standard itself. The commands are - dependent on the type of device at hand. It does not make much sense - of course to define a Write command for a scanner.</para> - - <para>The SCSI bus is a parallel bus, which comes in a number of - variants. The oldest and most used is an 8 bit wide bus, with - single-ended signals, carried on 50 wires. (If you do not know what - single-ended means, do not worry, that is what this document is all - about.) Modern designs also use 16 bit wide buses, with differential - signals. This allows transfer speeds of 20Mbytes/second, on cables - lengths of up to 25 meters. SCSI-2 allows a maximum bus width of 32 - bits, using an additional cable. Quickly emerging are Ultra SCSI (also - called Fast-20) and Ultra2 (also called Fast-40). Fast-20 is 20 - million transfers per second (20 Mbytes/sec on a 8 bit bus), Fast-40 - is 40 million transfers per second (40 Mbytes/sec on a 8 bit bus). - Most hard drives sold today are single-ended Ultra SCSI (8 or 16 - bits).</para> - - <para>Of course the SCSI bus not only has data lines, but also a number - of control signals. A very elaborate protocol is part of the standard - to allow multiple devices to share the bus in an efficient manner. In - SCSI-2, the data is always checked using a separate parity line. In - pre-SCSI-2 designs parity was optional.</para> - - <para>In SCSI-3 even faster bus types are introduced, along with a - serial SCSI busses that reduces the cabling overhead and allows a - higher maximum bus length. You might see names like SSA and - fibre channel in this context. None of the serial buses are currently - in widespread use (especially not in the typical FreeBSD environment). - For this reason the serial bus types are not discussed any - further.</para> - - <para>As you could have guessed from the description above, SCSI devices - are intelligent. They have to be to adhere to the SCSI standard - (which is over 2 inches thick BTW). So, for a hard disk drive for - instance you do not specify a head/cylinder/sector to address a - particular block, but simply the number of the block you want. - Elaborate caching schemes, automatic bad block replacement etc are all - made possible by this 'intelligent device' approach.</para> - - <para>On a SCSI bus, each possible pair of devices can communicate. - Whether their function allows this is another matter, but the standard - does not restrict it. To avoid signal contention, the 2 devices have - to arbitrate for the bus before using it.</para> - - <para>The philosophy of SCSI is to have a standard that allows - older-standard devices to work with newer-standard ones. So, an old - SCSI-1 device should normally work on a SCSI-2 bus. I say Normally, - because it is not absolutely sure that the implementation of an old - device follows the (old) standard closely enough to be acceptable on a - new bus. Modern devices are usually more well-behaved, because the - standardization has become more strict and is better adhered to by the - device manufacturers.</para> - - <para>Generally speaking, the chances of getting a working set of - devices on a single bus is better when all the devices are SCSI-2 or - newer. This implies that you do not have to dump all your old stuff - when you get that shiny 2GB disk: I own a system on which a pre-SCSI-1 - disk, a SCSI-2 QIC tape unit, a SCSI-1 helical scan tape unit and 2 - SCSI-1 disks work together quite happily. From a performance - standpoint you might want to separate your older and newer (=faster) - devices however.</para> - - <sect2> - <title>Components of SCSI</title> - - <para>As said before, SCSI devices are smart. The idea is to put the - knowledge about intimate hardware details onto the SCSI device - itself. In this way, the host system does not have to worry about - things like how many heads a hard disks has, or how many tracks - there are on a specific tape device. If you are curious, the - standard specifies commands with which you can query your devices on - their hardware particulars. FreeBSD uses this capability during - boot to check out what devices are connected and whether they need - any special treatment.</para> - - <para>The advantage of intelligent devices is obvious: the device - drivers on the host can be made in a much more generic fashion, - there is no longer a need to change (and qualify!) drivers for every - odd new device that is introduced.</para> - - <para>For cabling and connectors there is a golden rule: get good - stuff. With bus speeds going up all the time you will save yourself - a lot of grief by using good material.</para> - - <para>So, gold plated connectors, shielded cabling, sturdy connector - hoods with strain reliefs etc are the way to go. Second golden rule: - do no use cables longer than necessary. I once spent 3 days hunting - down a problem with a flaky machine only to discover that shortening - the SCSI bus by 1 meter solved the problem. And the original bus - length was well within the SCSI specification.</para> - </sect2> - - <sect2> - <title>SCSI bus types</title> - - <para>From an electrical point of view, there are two incompatible bus - types: single-ended and differential. This means that there are two - different main groups of SCSI devices and controllers, which cannot - be mixed on the same bus. It is possible however to use special - converter hardware to transform a single-ended bus into a - differential one (and vice versa). The differences between the bus - types are explained in the next sections.</para> - - <para>In lots of SCSI related documentation there is a sort of jargon - in use to abbreviate the different bus types. A small list:</para> - - <itemizedlist> - <listitem> - <para>FWD: Fast Wide Differential</para> - </listitem> - - <listitem> - <para>FND: Fast Narrow Differential</para> - </listitem> - - <listitem> - <para>SE: Single Ended</para> - </listitem> - - <listitem> - <para>FN: Fast Narrow</para> - </listitem> - - <listitem> - <para>etc.</para> - </listitem> - </itemizedlist> - - - <para>With a minor amount of imagination one can usually imagine what - is meant.</para> - - <para>Wide is a bit ambiguous, it can indicate 16 or 32 bit buses. As - far as I know, the 32 bit variant is not (yet) in use, so wide - normally means 16 bit.</para> - - <para>Fast means that the timing on the bus is somewhat different, so - that on a narrow (8 bit) bus 10 Mbytes/sec are possible instead of 5 - Mbytes/sec for 'slow' SCSI. As discussed before, bus speeds of 20 - and 40 million transfers/second are also emerging (Fast-20 == Ultra - SCSI and Fast-40 == Ultra2 SCSI).</para> - - <note> - <para>The data lines > 8 are only used for data transfers and - device addressing. The transfers of commands and status messages - etc are only performed on the lowest 8 data lines. The standard - allows narrow devices to operate on a wide bus. The usable bus - width is negotiated between the devices. You have to watch your - device addressing closely when mixing wide and narrow.</para> - </note> - - <sect3> - <title>Single ended buses</title> - - <para>A single-ended SCSI bus uses signals that are either 5 Volts - or 0 Volts (indeed, TTL levels) and are relative to a COMMON - ground reference. A singled ended 8 bit SCSI bus has - approximately 25 ground lines, who are all tied to a single `rail' - on all devices. A standard single ended bus has a maximum length - of 6 meters. If the same bus is used with fast-SCSI devices, the - maximum length allowed drops to 3 meters. Fast-SCSI means that - instead of 5Mbytes/sec the bus allows 10Mbytes/sec - transfers.</para> - - <para>Fast-20 (Ultra SCSI) and Fast-40 allow for 20 and 40 million - transfers/second respectively. So, F20 is 20 Mbytes/second on a 8 - bit bus, 40 Mbytes/second on a 16 bit bus etc. For F20 the max - bus length is 1.5 meters, for F40 it becomes 0.75 meters. Be - aware that F20 is pushing the limits quite a bit, so you will - quickly find out if your SCSI bus is electrically sound.</para> - - <note> - <para>If some devices on your bus use 'fast' to communicate your - bus must adhere to the length restrictions for fast - buses!</para> - </note> - - <para>It is obvious that with the newer fast-SCSI devices the bus - length can become a real bottleneck. This is why the differential - SCSI bus was introduced in the SCSI-2 standard.</para> - - <para>For connector pinning and connector types please refer to the - SCSI-2 standard (see <link linkend="scsi-further-reading">Further - reading</link>) itself, connectors etc are listed there in - painstaking detail.</para> - - <para>Beware of devices using non-standard cabling. For instance - Apple uses a 25pin D-type connecter (like the one on serial ports - and parallel printers). Considering that the official SCSI bus - needs 50 pins you can imagine the use of this connector needs some - 'creative cabling'. The reduction of the number of ground wires - they used is a bad idea, you better stick to 50 pins cabling in - accordance with the SCSI standard. For Fast-20 and 40 do not even - think about buses like this.</para> - </sect3> - - <sect3> - <title>Differential buses</title> - - <para>A differential SCSI bus has a maximum length of 25 meters. - Quite a difference from the 3 meters for a single-ended fast-SCSI - bus. The idea behind differential signals is that each bus signal - has its own return wire. So, each signal is carried on a - (preferably twisted) pair of wires. The voltage difference - between these two wires determines whether the signal is asserted - or de-asserted. To a certain extent the voltage difference - between ground and the signal wire pair is not relevant (do not - try 10 kVolts though).</para> - - <para>It is beyond the scope of this document to explain why this - differential idea is so much better. Just accept that - electrically seen the use of differential signals gives a much - better noise margin. You will normally find differential buses in - use for inter-cabinet connections. Because of the lower cost - single ended is mostly used for shorter buses like inside - cabinets.</para> - - <para>There is nothing that stops you from using differential stuff - with FreeBSD, as long as you use a controller that has device - driver support in FreeBSD. As an example, Adaptec marketed the - AHA1740 as a single ended board, whereas the AHA1744 was - differential. The software interface to the host is identical for - both.</para> - </sect3> - - <sect3> - <title>Terminators</title> - - <para>Terminators in SCSI terminology are resistor networks that are - used to get a correct impedance matching. Impedance matching is - important to get clean signals on the bus, without reflections or - ringing. If you once made a long distance telephone call on a bad - line you probably know what reflections are. With 20Mbytes/sec - traveling over your SCSI bus, you do not want signals echoing - back.</para> - - <para>Terminators come in various incarnations, with more or less - sophisticated designs. Of course, there are internal and external - variants. Many SCSI devices come with a number of sockets in - which a number of resistor networks can (must be!) installed. If - you remove terminators from a device, carefully store them. You - will need them when you ever decide to reconfigure your SCSI bus. - There is enough variation in even these simple tiny things to make - finding the exact replacement a frustrating business. There are - also SCSI devices that have a single jumper to enable or disable a - built-in terminator. There are special terminators you can stick - onto a flat cable bus. Others look like external connectors, or a - connector hood without a cable. So, lots of choice as you can - see.</para> - - <para>There is much debate going on if and when you should switch - from simple resistor (passive) terminators to active terminators. - Active terminators contain slightly more elaborate circuit to give - cleaner bus signals. The general consensus seems to be that the - usefulness of active termination increases when you have long - buses and/or fast devices. If you ever have problems with your - SCSI buses you might consider trying an active terminator. Try to - borrow one first, they reputedly are quite expensive.</para> - - <para>Please keep in mind that terminators for differential and - single-ended buses are not identical. You should <emphasis>not - mix</emphasis> the two variants.</para> - - <para>OK, and now where should you install your terminators? This is - by far the most misunderstood part of SCSI. And it is by far the - simplest. The rule is: <emphasis>every single line on the SCSI - bus has 2 (two) terminators, one at each end of the - bus.</emphasis> So, two and not one or three or whatever. Do - yourself a favor and stick to this rule. It will save you endless - grief, because wrong termination has the potential to introduce - highly mysterious bugs. (Note the <quote>potential</quote> here; - the nastiest part is that it may or may not work.)</para> - - <para>A common pitfall is to have an internal (flat) cable in a - machine and also an external cable attached to the controller. It - seems almost everybody forgets to remove the terminators from the - controller. The terminator must now be on the last external - device, and not on the controller! In general, every - reconfiguration of a SCSI bus must pay attention to this.</para> - - <note> - <para>Termination is to be done on a per-line basis. This means - if you have both narrow and wide buses connected to the same - host adapter, you need to enable termination on the higher 8 - bits of the bus on the adapter (as well as the last devices on - each bus, of course).</para> - </note> - - <para>What I did myself is remove all terminators from my SCSI - devices and controllers. I own a couple of external terminators, - for both the Centronics-type external cabling and for the internal - flat cable connectors. This makes reconfiguration much - easier.</para> - - <para>On modern devices, sometimes integrated terminators are used. - These things are special purpose integrated circuits that can be - enabled or disabled with a control pin. It is not necessary to - physically remove them from a device. You may find them on newer - host adapters, sometimes they are software configurable, using - some sort of setup tool. Some will even auto-detect the cables - attached to the connectors and automatically set up the - termination as necessary. At any rate, consult your - documentation!</para> - </sect3> - - <sect3> - <title>Terminator power</title> - - <para>The terminators discussed in the previous chapter need power - to operate properly. On the SCSI bus, a line is dedicated to this - purpose. So, simple huh?</para> - - <para>Not so. Each device can provide its own terminator power to - the terminator sockets it has on-device. But if you have external - terminators, or when the device supplying the terminator power to - the SCSI bus line is switched off you are in trouble.</para> - - <para>The idea is that initiators (these are devices that initiate - actions on the bus, a discussion follows) must supply terminator - power. All SCSI devices are allowed (but not required) to supply - terminator power.</para> - - <para>To allow for un-powered devices on a bus, the terminator power - must be supplied to the bus via a diode. This prevents the - backflow of current to un-powered devices.</para> - - <para>To prevent all kinds of nastiness, the terminator power is - usually fused. As you can imagine, fuses might blow. This can, - but does not have to, lead to a non functional bus. If multiple - devices supply terminator power, a single blown fuse will not put - you out of business. A single supplier with a blown fuse - certainly will. Clever external terminators sometimes have a LED - indication that shows whether terminator power is present.</para> - - <para>In newer designs auto-restoring fuses that 'reset' themselves - after some time are sometimes used.</para> - </sect3> - - <sect3> - <title>Device addressing</title> - - <para>Because the SCSI bus is, ehh, a bus there must be a way to - distinguish or address the different devices connected to - it.</para> - - <para>This is done by means of the SCSI or target ID. Each device - has a unique target ID. You can select the ID to which a device - must respond using a set of jumpers, or a dip switch, or something - similar. Some SCSI host adapters let you change the target ID - from the boot menu. (Yet some others will not let you change the - ID from 7.) Consult the documentation of your device for more - information.</para> - - <para>Beware of multiple devices configured to use the same ID. - Chaos normally reigns in this case. A pitfall is that one of the - devices sharing the same ID sometimes even manages to answer to - I/O requests!</para> - - <para>For an 8 bit bus, a maximum of 8 targets is possible. The - maximum is 8 because the selection is done bitwise using the 8 - data lines on the bus. For wide buses this increases to the - number of data lines (usually 16).</para> - - <note> - <para>A narrow SCSI device can not communicate with a SCSI device - with a target ID larger than 7. This means it is generally not - a good idea to move your SCSI host adapter's target ID to - something higher than 7 (or your CDROM will stop - working).</para> - </note> - - <para>The higher the SCSI target ID, the higher the priority the - devices has. When it comes to arbitration between devices that - want to use the bus at the same time, the device that has the - highest SCSI ID will win. This also means that the SCSI host - adapter usually uses target ID 7. Note however that the lower 8 - IDs have higher priorities than the higher 8 IDs on a wide-SCSI - bus. Thus, the order of target IDs is: [7 6 .. 1 0 15 14 .. 9 8] - on a wide-SCSI system. (If you are wondering why the lower 8 - have higher priority, read the previous paragraph for a - hint.)</para> - - <para>For a further subdivision, the standard allows for Logical - Units or LUNs for short. A single target ID may have multiple - LUNs. For example, a tape device including a tape changer may - have LUN 0 for the tape device itself, and LUN 1 for the tape - changer. In this way, the host system can address each of the - functional units of the tape changer as desired.</para> - </sect3> - - <sect3> - <title>Bus layout</title> - - <para>SCSI buses are linear. So, not shaped like Y-junctions, star - topologies, rings, cobwebs or whatever else people might want to - invent. One of the most common mistakes is for people with - wide-SCSI host adapters to connect devices on all three connecters - (external connector, internal wide connector, internal narrow - connector). Don't do that. It may appear to work if you are - really lucky, but I can almost guarantee that your system will - stop functioning at the most unfortunate moment (this is also - known as <quote>Murphy's law</quote>).</para> - - <para>You might notice that the terminator issue discussed earlier - becomes rather hairy if your bus is not linear. Also, if you have - more connectors than devices on your internal SCSI cable, make - sure you attach devices on connectors on both ends instead of - using the connectors in the middle and let one or both ends - dangle. This will screw up the termination of the bus.</para> - - <para>The electrical characteristics, its noise margins and - ultimately the reliability of it all are tightly related to linear - bus rule.</para> - - <para><emphasis>Stick to the linear bus rule!</emphasis></para> - </sect3> - </sect2> - - <sect2> - <title>Using SCSI with FreeBSD</title> - - <sect3> - <title>About translations, BIOSes and magic...</title> - - <para>As stated before, you should first make sure that you have a - electrically sound bus.</para> - - <para>When you want to use a SCSI disk on your PC as boot disk, you - must aware of some quirks related to PC BIOSes. The PC BIOS in - its first incarnation used a low level physical interface to the - hard disk. So, you had to tell the BIOS (using a setup tool or a - BIOS built-in setup) how your disk physically looked like. This - involved stating number of heads, number of cylinders, number of - sectors per track, obscure things like precompensation and reduced - write current cylinder etc.</para> - - <para>One might be inclined to think that since SCSI disks are smart - you can forget about this. Alas, the arcane setup issue is still - present today. The system BIOS needs to know how to access your - SCSI disk with the head/cyl/sector method in order to load the - FreeBSD kernel during boot.</para> - - <para>The SCSI host adapter or SCSI controller you have put in your - AT/EISA/PCI/whatever bus to connect your disk therefore has its - own on-board BIOS. During system startup, the SCSI BIOS takes - over the hard disk interface routines from the system BIOS. To - fool the system BIOS, the system setup is normally set to No hard - disk present. Obvious, isn't it?</para> - - <para>The SCSI BIOS itself presents to the system a so called - <emphasis>translated</emphasis> drive. This means that a fake - drive table is constructed that allows the PC to boot the drive. - This translation is often (but not always) done using a pseudo - drive with 64 heads and 32 sectors per track. By varying the - number of cylinders, the SCSI BIOS adapts to the actual drive - size. It is useful to note that 32 * 64 / 2 = the size of your - drive in megabytes. The division by 2 is to get from disk blocks - that are normally 512 bytes in size to Kbytes.</para> - - <para>Right. All is well now?! No, it is not. The system BIOS has - another quirk you might run into. The number of cylinders of a - bootable hard disk cannot be greater than 1024. Using the - translation above, this is a show-stopper for disks greater than 1 - GB. With disk capacities going up all the time this is causing - problems.</para> - - <para>Fortunately, the solution is simple: just use another - translation, e.g. with 128 heads instead of 32. In most cases new - SCSI BIOS versions are available to upgrade older SCSI host - adapters. Some newer adapters have an option, in the form of a - jumper or software setup selection, to switch the translation the - SCSI BIOS uses.</para> - - <para>It is very important that <emphasis>all</emphasis> operating - systems on the disk use the <emphasis>same translation</emphasis> - to get the right idea about where to find the relevant partitions. - So, when installing FreeBSD you must answer any questions about - heads/cylinders etc using the translated values your host adapter - uses.</para> - - <para>Failing to observe the translation issue might lead to - un-bootable systems or operating systems overwriting each others - partitions. Using fdisk you should be able to see all - partitions.</para> - - <para>You might have heard some talk of <quote>lying</quote> devices? - Older FreeBSD kernels used to report the geometry of SCSI disks - when booting. An example from one of my systems:</para> - - <screen>aha0 targ 0 lun 0: <MICROP 1588-15MB1057404HSP4> -sd0: 636MB (1303250 total sec), 1632 cyl, 15 head, 53 sec, bytes/sec 512</screen> - - <para>Newer kernels usually do not report this information. - e.g.</para> - - <screen>(bt0:0:0): "SEAGATE ST41651 7574" type 0 fixed SCSI 2 -sd0(bt0:0:0): Direct-Access 1350MB (2766300 512 byte sectors)</screen> - - <para>Why has this changed?</para> - - <para>This info is retrieved from the SCSI disk itself. Newer disks - often use a technique called zone bit recording. The idea is that - on the outer cylinders of the drive there is more space so more - sectors per track can be put on them. This results in disks that - have more tracks on outer cylinders than on the inner cylinders - and, last but not least, have more capacity. You can imagine that - the value reported by the drive when inquiring about the geometry - now becomes suspect at best, and nearly always misleading. When - asked for a geometry , it is nearly always better to supply the - geometry used by the BIOS, or <emphasis>if the BIOS is never going - to know about this disk</emphasis>, (e.g. it is not a booting - disk) to supply a fictitious geometry that is convenient.</para> - </sect3> - - <sect3> - <title>SCSI subsystem design</title> - - <para>FreeBSD uses a layered SCSI subsystem. For each different - controller card a device driver is written. This driver knows all - the intimate details about the hardware it controls. The driver - has a interface to the upper layers of the SCSI subsystem through - which it receives its commands and reports back any status.</para> - - <para>On top of the card drivers there are a number of more generic - drivers for a class of devices. More specific: a driver for tape - devices (abbreviation: st), magnetic disks (sd), CDROMs (cd) etc. - In case you are wondering where you can find this stuff, it all - lives in <filename>/sys/scsi</filename>. See the man pages in - section 4 for more details.</para> - - <para>The multi level design allows a decoupling of low-level bit - banging and more high level stuff. Adding support for another - piece of hardware is a much more manageable problem.</para> - </sect3> - - <sect3> - <title>Kernel configuration</title> - - <para>Dependent on your hardware, the kernel configuration file must - contain one or more lines describing your host adapter(s). This - includes I/O addresses, interrupts etc. Consult the man page for - your adapter driver to get more info. Apart from that, check out - <filename>/sys/i386/conf/LINT</filename> for an overview of a - kernel config file. <filename>LINT</filename> contains every - possible option you can dream of. It does - <emphasis>not</emphasis> imply <filename>LINT</filename> will - actually get you to a working kernel at all.</para> - - <para>Although it is probably stating the obvious: the kernel config - file should reflect your actual hardware setup. So, interrupts, - I/O addresses etc must match the kernel config file. During - system boot messages will be displayed to indicate whether the - configured hardware was actually found.</para> - - <note> - <para>Note that most of the EISA/PCI drivers (namely - <devicename>ahb</devicename>, <devicename>ahc</devicename>, - <devicename>ncr</devicename> and <devicename>amd</devicename> - will automatically obtain the correct parameters from the host - adapters themselves at boot time; thus, you just need to write, - for instance, <literal>controller ahc0</literal>.</para> - </note> - - <para>An example loosely based on the FreeBSD 2.2.5-Release kernel - config file <filename>LINT</filename> with some added comments - (between []):</para> - - <programlisting># SCSI host adapters: `aha', `ahb', `aic', `bt', `nca' -# -# aha: Adaptec 154x -# ahb: Adaptec 174x -# ahc: Adaptec 274x/284x/294x -# aic: Adaptec 152x and sound cards using the Adaptec AIC-6360 (slow!) -# amd: AMD 53c974 based SCSI cards (e.g., Tekram DC-390 and 390T) -# bt: Most Buslogic controllers -# nca: ProAudioSpectrum cards using the NCR 5380 or Trantor T130 -# ncr: NCR/Symbios 53c810/815/825/875 etc based SCSI cards -# uha: UltraStore 14F and 34F -# sea: Seagate ST01/02 8 bit controller (slow!) -# wds: Western Digital WD7000 controller (no scatter/gather!). -# - -[For an Adaptec AHA274x/284x/294x/394x etc controller] -controller ahc0 - -[For an NCR/Symbios 53c875 based controller] -controller ncr0 - -[For an Ultrastor adapter] -controller uha0 at isa? port "IO_UHA0" bio irq ? drq 5 vector uhaintr - -# Map SCSI buses to specific SCSI adapters -controller scbus0 at ahc0 -controller scbus2 at ncr0 -controller scbus1 at uha0 - -# The actual SCSI devices -disk sd0 at scbus0 target 0 unit 0 [SCSI disk 0 is at scbus 0, LUN 0] -disk sd1 at scbus0 target 1 [implicit LUN 0 if omitted] -disk sd2 at scbus1 target 3 [SCSI disk on the uha0] -disk sd3 at scbus2 target 4 [SCSI disk on the ncr0] -tape st1 at scbus0 target 6 [SCSI tape at target 6] -device cd0 at scbus? [the first ever CDROM found, no wiring]</programlisting> - - <para>The example above tells the kernel to look for a ahc (Adaptec - 274x) controller, then for an NCR/Symbios board, and so on. The - lines following the controller specifications tell the kernel to - configure specific devices but <emphasis>only</emphasis> attach - them when they match the target ID and LUN specified on the - corresponding bus.</para> - - <para>Wired down devices get <quote>first shot</quote> at the unit - numbers so the first non <quote>wired down</quote> device, is - allocated the unit number one greater than the highest - <quote>wired down</quote> unit number for that kind of device. So, - if you had a SCSI tape at target ID 2 it would be configured as - st2, as the tape at target ID 6 is wired down to unit number - 1.</para> - - <note> - <para>Wired down devices need not be found to get their unit - number. The unit number for a wired down device is reserved for - that device, even if it is turned off at boot time. This allows - the device to be turned on and brought on-line at a later time, - without rebooting. Notice that a device's unit number has - <emphasis>no</emphasis> relationship with its target ID on the - SCSI bus.</para> - </note> - - <para>Below is another example of a kernel config file as used by - FreeBSD version < 2.0.5. The difference with the first example - is that devices are not <quote>wired down</quote>. <quote>Wired - down</quote> means that you specify which SCSI target belongs to - which device.</para> - - <para>A kernel built to the config file below will attach the first - SCSI disk it finds to sd0, the second disk to sd1 etc. If you ever - removed or added a disk, all other devices of the same type (disk - in this case) would 'move around'. This implies you have to - change <filename>/etc/fstab</filename> each time.</para> - - <para>Although the old style still works, you are - <emphasis>strongly</emphasis> recommended to use this new feature. - It will save you a lot of grief whenever you shift your hardware - around on the SCSI buses. So, when you re-use your old trusty - config file after upgrading from a pre-FreeBSD2.0.5.R system check - this out.</para> - - <programlisting>[driver for Adaptec 174x] -controller ahb0 at isa? bio irq 11 vector ahbintr - -[for Adaptec 154x] -controller aha0 at isa? port "IO_AHA0" bio irq 11 drq 5 vector ahaintr - -[for Seagate ST01/02] -controller sea0 at isa? bio irq 5 iomem 0xc8000 iosiz 0x2000 vector seaintr - -controller scbus0 - -device sd0 [support for 4 SCSI harddisks, sd0 up sd3] -device st0 [support for 2 SCSI tapes] - -[for the CDROM] -device cd0 #Only need one of these, the code dynamically grows</programlisting> - - <para>Both examples support SCSI disks. If during boot more devices - of a specific type (e.g. sd disks) are found than are configured - in the booting kernel, the system will simply allocate more - devices, incrementing the unit number starting at the last number - <quote>wired down</quote>. If there are no <quote>wired - down</quote> devices then counting starts at unit 0.</para> - - <para>Use <command>man 4 scsi</command> to check for the latest info - on the SCSI subsystem. For more detailed info on host adapter - drivers use e.g., <command>man 4 ahc</command> for info on the - Adaptec 294x driver.</para> - </sect3> - - <sect3> - <title>Tuning your SCSI kernel setup</title> - - <para>Experience has shown that some devices are slow to respond to - INQUIRY commands after a SCSI bus reset (which happens at boot - time). An INQUIRY command is sent by the kernel on boot to see - what kind of device (disk, tape, CDROM etc.) is connected to a - specific target ID. This process is called device probing by the - way.</para> - - <para>To work around the 'slow response' problem, FreeBSD allows a - tunable delay time before the SCSI devices are probed following a - SCSI bus reset. You can set this delay time in your kernel - configuration file using a line like:</para> - - <programlisting>options SCSI_DELAY=15 #Be pessimistic about Joe SCSI device</programlisting> - - <para>This line sets the delay time to 15 seconds. On my own system - I had to use 3 seconds minimum to get my trusty old CDROM drive - to be recognized. Start with a high value (say 30 seconds or so) - when you have problems with device recognition. If this helps, - tune it back until it just stays working.</para> - </sect3> - - <sect3 id="scsi-rogue-devices"> - <title>Rogue SCSI devices</title> - - <para>Although the SCSI standard tries to be complete and concise, - it is a complex standard and implementing things correctly is no - easy task. Some vendors do a better job then others.</para> - - <para>This is exactly where the <quote>rogue</quote> devices come - into view. Rogues are devices that are recognized by the FreeBSD - kernel as behaving slightly (...) non-standard. Rogue devices are - reported by the kernel when booting. An example for two of my - cartridge tape units:</para> - - <screen>Feb 25 21:03:34 yedi /kernel: ahb0 targ 5 lun 0: <TANDBERG TDC 3600 -06:> -Feb 25 21:03:34 yedi /kernel: st0: Tandberg tdc3600 is a known rogue - -Mar 29 21:16:37 yedi /kernel: aha0 targ 5 lun 0: <ARCHIVE VIPER 150 21247-005> -Mar 29 21:16:37 yedi /kernel: st1: Archive Viper 150 is a known rogue </screen> - - <para>For instance, there are devices that respond to all LUNs on a - certain target ID, even if they are actually only one device. It - is easy to see that the kernel might be fooled into believing that - there are 8 LUNs at that particular target ID. The confusion this - causes is left as an exercise to the reader.</para> - - <para>The SCSI subsystem of FreeBSD recognizes devices with bad - habits by looking at the INQUIRY response they send when probed. - Because the INQUIRY response also includes the version number of - the device firmware, it is even possible that for different - firmware versions different workarounds are used. See e.g. - <filename>/sys/scsi/st.c</filename> and - <filename>/sys/scsi/scsiconf.c</filename> for more info on how - this is done.</para> - - <para>This scheme works fine, but keep in mind that it of course - only works for devices that are known to be weird. If you are the - first to connect your bogus Mumbletech SCSI CDROM you might be - the one that has to define which workaround is needed.</para> - - <para>After you got your Mumbletech working, please send the - required workaround to the FreeBSD development team for inclusion - in the next release of FreeBSD. Other Mumbletech owners will be - grateful to you.</para> - </sect3> - - <sect3> - <title>Multiple LUN devices</title> - - <para>In some cases you come across devices that use multiple - logical units (LUNs) on a single SCSI ID. In most cases FreeBSD - only probes devices for LUN 0. An example are so called bridge - boards that connect 2 non-SCSI harddisks to a SCSI bus (e.g. an - Emulex MD21 found in old Sun systems).</para> - - <para>This means that any devices with LUNs != 0 are not normally - found during device probe on system boot. To work around this - problem you must add an appropriate entry in /sys/scsi/scsiconf.c - and rebuild your kernel.</para> - - <para>Look for a struct that is initialized like below:</para> - - <programlisting>{ - T_DIRECT, T_FIXED, "MAXTOR", "XT-4170S", "B5A", - "mx1", SC_ONE_LU -}</programlisting> - - <para>For you Mumbletech BRIDGE2000 that has more than one LUN, acts - as a SCSI disk and has firmware revision 123 you would add - something like:</para> - - <programlisting>{ - T_DIRECT, T_FIXED, "MUMBLETECH", "BRIDGE2000", "123", - "sd", SC_MORE_LUS -}</programlisting> - - <para>The kernel on boot scans the inquiry data it receives against - the table and acts accordingly. See the source for more - info.</para> - </sect3> - - <sect3> - <title>Tagged command queuing</title> - - <para>Modern SCSI devices, particularly magnetic disks, - support what is called tagged command queuing (TCQ).</para> - - <para>In a nutshell, TCQ allows the device to have multiple I/O - requests outstanding at the same time. Because the device is - intelligent, it can optimize its operations (like head - positioning) based on its own request queue. On SCSI devices - like RAID (Redundant Array of Independent Disks) arrays the TCQ - function is indispensable to take advantage of the device's - inherent parallelism.</para> - - <para>Each I/O request is uniquely identified by a <quote>tag</quote> - (hence the name tagged command queuing) and this tag is used by - FreeBSD to see which I/O in the device drivers queue is reported - as complete by the device.</para> - - <para>It should be noted however that TCQ requires device driver - support and that some devices implemented it <quote>not quite - right</quote> in their firmware. This problem bit me once, and it - leads to highly mysterious problems. In such cases, try to - disable TCQ.</para> - </sect3> - - <sect3> - <title>Busmaster host adapters</title> - - <para>Most, but not all, SCSI host adapters are bus mastering - controllers. This means that they can do I/O on their own without - putting load onto the host CPU for data movement.</para> - - <para>This is of course an advantage for a multitasking operating - system like FreeBSD. It must be noted however that there might be - some rough edges.</para> - - <para>For instance an Adaptec 1542 controller can be set to use - different transfer speeds on the host bus (ISA or AT in this - case). The controller is settable to different rates because not - all motherboards can handle the higher speeds. Problems like - hang-ups, bad data etc might be the result of using a higher data - transfer rate then your motherboard can stomach.</para> - - <para>The solution is of course obvious: switch to a lower data - transfer rate and try if that works better.</para> - - <para>In the case of a Adaptec 1542, there is an option that can be - put into the kernel config file to allow dynamic determination of - the right, read: fastest feasible, transfer rate. This option is - disabled by default:</para> - - <programlisting>options "TUNE_1542" #dynamic tune of bus DMA speed</programlisting> - - <para>Check the man pages for the host adapter that you use. Or - better still, use the ultimate documentation (read: driver - source).</para> - </sect3> - </sect2> - - <sect2> - <title>Tracking down problems</title> - - <para>The following list is an attempt to give a guideline for the - most common SCSI problems and their solutions. It is by no means - complete.</para> - - <itemizedlist> - <listitem> - <para>Check for loose connectors and cables.</para> - </listitem> - - <listitem> - <para>Check and double check the location and number of your - terminators.</para> - </listitem> - - <listitem> - <para>Check if your bus has at least one supplier of terminator - power (especially with external terminators.</para> - </listitem> - - <listitem> - <para>Check if no double target IDs are used.</para> - </listitem> - - <listitem> - <para>Check if all devices to be used are powered up.</para> - </listitem> - - <listitem> - <para>Make a minimal bus config with as little devices as - possible.</para> - </listitem> - - <listitem> - <para>If possible, configure your host adapter to use slow bus - speeds.</para> - </listitem> - - <listitem> - <para>Disable tagged command queuing to make things as simple as - possible (for a NCR host adapter based system see man - ncrcontrol)</para> - </listitem> - - <listitem> - <para>If you can compile a kernel, make one with the - <literal>SCSIDEBUG</literal> option, and try accessing the - device with debugging turned on for that device. If your device - does not even probe at startup, you may have to define the - address of the device that is failing, and the desired debug - level in <filename>/sys/scsi/scsidebug.h</filename>. If it - probes but just does not work, you can use the - &man.scsi.8; command to dynamically set a debug level to - it in a running kernel (if <literal>SCSIDEBUG</literal> is - defined). This will give you <emphasis>copious</emphasis> - debugging output with which to confuse the gurus. See - <command>man 4 scsi</command> for more exact information. Also - look at <command>man 8 scsi</command>.</para> - </listitem> - </itemizedlist> - </sect2> - - <sect2 id="scsi-further-reading"> - <title>Further reading</title> - - <para>If you intend to do some serious SCSI hacking, you might want to - have the official standard at hand:</para> - - <para>Approved American National Standards can be purchased from - ANSI at - - <address> - <otheraddr>13th Floor</otheraddr> - <street>11 West 42nd Street</street> - <city>New York</city> - <state>NY</state> <postcode>10036</postcode> - Sales Dept: <phone>(212) 642-4900</phone> - </address> - </para> - - <para>You can also buy many ANSI - standards and most committee draft documents from Global - Engineering Documents, - - <address> - <street>15 Inverness Way East</street> - <city>Englewood</city> - <state>CO</state>, <postcode>80112-5704</postcode> - Phone: <phone>(800) 854-7179</phone> - Outside USA and Canada: <phone>(303) 792-2181</phone> - Fax: <fax>(303) 792- 2192</fax> - </address> - </para> - - <para>Many X3T10 draft documents are available electronically on the - SCSI BBS (719-574-0424) and on the <hostid - role="fqdn">ncrinfo.ncr.com</hostid> anonymous FTP site.</para> - - <para>Latest X3T10 committee documents are:</para> - - <itemizedlist> - <listitem> - <para>AT Attachment (ATA or IDE) [X3.221-1994] - (<emphasis>Approved</emphasis>)</para> - </listitem> - - <listitem> - <para>ATA Extensions (ATA-2) [X3T10/948D Rev 2i]</para> - </listitem> - - <listitem> - <para>Enhanced Small Device Interface (ESDI) - [X3.170-1990/X3.170a-1991] - (<emphasis>Approved</emphasis>)</para> - </listitem> - - <listitem> - <para>Small Computer System Interface — 2 (SCSI-2) - [X3.131-1994] (<emphasis>Approved</emphasis>)</para> - </listitem> - - <listitem> - <para>SCSI-2 Common Access Method Transport and SCSI Interface - Module (CAM) [X3T10/792D Rev 11]</para> - </listitem> - </itemizedlist> - - <para>Other publications that might provide you with additional - information are:</para> - - <itemizedlist> - <listitem> - <para><quote>SCSI: Understanding the Small Computer System - Interface</quote>, written by NCR Corporation. Available from: - Prentice Hall, Englewood Cliffs, NJ, 07632 Phone: (201) 767-5937 - ISBN 0-13-796855-8</para> - </listitem> - - <listitem> - <para><quote>Basics of SCSI</quote>, a SCSI tutorial written by - Ancot Corporation Contact Ancot for availability information at: - Phone: (415) 322-5322 Fax: (415) 322-0455</para> - </listitem> - - <listitem> - <para><quote>SCSI Interconnection Guide Book</quote>, an AMP - publication (dated 4/93, Catalog 65237) that lists the various - SCSI connectors and suggests cabling schemes. Available from - AMP at (800) 522-6752 or (717) 564-0100</para> - </listitem> - - <listitem> - <para><quote>Fast Track to SCSI</quote>, A Product Guide written by - Fujitsu. Available from: Prentice Hall, Englewood Cliffs, NJ, - 07632 Phone: (201) 767-5937 ISBN 0-13-307000-X</para> - </listitem> - - <listitem> - <para><quote>The SCSI Bench Reference</quote>, <quote>The SCSI - Encyclopedia</quote>, and the <quote>SCSI Tutor</quote>, ENDL - Publications, 14426 Black Walnut Court, Saratoga CA, 95070 - Phone: (408) 867-6642</para> - </listitem> - - <listitem> - <para><quote>Zadian SCSI Navigator</quote> (quick ref. book) and - <quote>Discover the Power of SCSI</quote> (First book along with - a one-hour video and tutorial book), Zadian Software, Suite 214, - 1210 S. Bascom Ave., San Jose, CA 92128, (408) 293-0800</para> - </listitem> - </itemizedlist> - - <para>On Usenet the newsgroups <ulink - url="news:comp.periphs.scsi">comp.periphs.scsi</ulink> and <ulink - url="news:comp.periphs">comp.periphs</ulink> are noteworthy places - to look for more info. You can also find the SCSI-Faq there, which - is posted periodically.</para> - - <para>Most major SCSI device and host adapter suppliers operate FTP - sites and/or BBS systems. They may be valuable sources of - information about the devices you own.</para> - </sect2> - </sect1> - - <sect1 id="hw-storage-controllers"> - <title>* Disk/tape controllers</title> - - <sect2> - <title>* SCSI</title> - - <para></para> - </sect2> - - <sect2> - <title>* IDE</title> - - <para></para> - </sect2> - - <sect2> - <title>* Floppy</title> - - <para></para> - </sect2> - </sect1> - - <sect1> - <title>Hard drives</title> - - <sect2> - <title>SCSI hard drives</title> - - <para><emphasis>Contributed by &a.asami;. 17 February - 1998.</emphasis></para> - - <para>As mentioned in the <link linkend="scsi">SCSI</link> section, - virtually all SCSI hard drives sold today are SCSI-2 compliant and - thus will work fine as long as you connect them to a supported SCSI - host adapter. Most problems people encounter are either due to - badly designed cabling (cable too long, star topology, etc.), - insufficient termination, or defective parts. Please refer to the - <link linkend="scsi">SCSI</link> section first if your SCSI hard - drive is not working. However, there are a couple of things you may - want to take into account before you purchase SCSI hard drives for - your system.</para> - - <sect3> - <title>Rotational speed</title> - - <para>Rotational speeds of SCSI drives sold today range from around - 4,500RPM to 10,000RPM. Most of them are either 5,400RPM or - 7,200RPM. Even though the 7,200RPM drives can generally transfer - data faster, they run considerably hotter than their 5,400RPM - counterparts. A large fraction of today's disk drive malfunctions - are heat-related. If you do not have very good cooling in your PC - case, you may want to stick with 5,400RPM or slower drives.</para> - - <para>Note that newer drives, with higher areal recording densities, - can deliver much more bits per rotation than older ones. Today's - top-of-line 5,400RPM drives can sustain a throughput comparable to - 7,200RPM drives of one or two model generations ago. The number - to find on the spec sheet for bandwidth is <quote>internal data - (or transfer) rate</quote>. It is usually in megabits/sec so - divide it by 8 and you'll get the rough approximation of how much - megabytes/sec you can get out of the drive.</para> - - <para>(If you are a speed maniac and want a 10,000RPM drive for your - cute little PC, be my guest; however, those drives become - extremely hot. Don't even think about it if you don't have a fan - blowing air <emphasis>directly at</emphasis> the drive or a - properly ventilated disk enclosure.)</para> - - <para>Obviously, the latest 10,000RPM drives and 7,200RPM drives can - deliver more data than the latest 5,400RPM drives, so if absolute - bandwidth is the necessity for your applications, you have little - choice but to get the faster drives. Also, if you need low - latency, faster drives are better; not only do they usually have - lower average seek times, but also the rotational delay is one - place where slow-spinning drives can never beat a faster one. - (The average rotational latency is half the time it takes to - rotate the drive once; thus, it's 3 milliseconds for 10,000RPM - drives, 4.2ms for 7,200RPM drives and 5.6ms for 5,400RPM drives.) - Latency is seek time plus rotational delay. Make sure you - understand whether you need low latency or more accesses per - second, though; in the latter case (e.g., news servers), it may - not be optimal to purchase one big fast drive. You can achieve - similar or even better results by using the ccd (concatenated - disk) driver to create a striped disk array out of multiple slower - drives for comparable overall cost.</para> - - <para>Make sure you have adequate air flow around the drive, - especially if you are going to use a fast-spinning drive. You - generally need at least 1/2" (1.25cm) of spacing above and below a - drive. Understand how the air flows through your PC case. Most - cases have the power supply suck the air out of the back. See - where the air flows in, and put the drive where it will have the - largest volume of cool air flowing around it. You may need to seal - some unwanted holes or add a new fan for effective cooling.</para> - - <para>Another consideration is noise. Many 7,200 or faster drives - generate a high-pitched whine which is quite unpleasant to most - people. That, plus the extra fans often required for cooling, may - make 7,200 or faster drives unsuitable for some office and home - environments.</para> - </sect3> - - <sect3> - <title>Form factor</title> - - <para>Most SCSI drives sold today are of 3.5" form factor. They - come in two different heights; 1.6" (<quote>half-height</quote>) or - 1" (<quote>low-profile</quote>). The half-height drive is the same - height as a CDROM drive. However, don't forget the spacing rule - mentioned in the previous section. If you have three standard - 3.5" drive bays, you will not be able to put three half-height - drives in there (without frying them, that is).</para> - </sect3> - - <sect3> - <title>Interface</title> - - <para>The majority of SCSI hard drives sold today are Ultra or - Ultra-wide SCSI. The maximum bandwidth of Ultra SCSI is 20MB/sec, - and Ultra-wide SCSI is 40MB/sec. There is no difference in max - cable length between Ultra and Ultra-wide; however, the more - devices you have on the same bus, the sooner you will start having - bus integrity problems. Unless you have a well-designed disk - enclosure, it is not easy to make more than 5 or 6 Ultra SCSI - drives work on a single bus.</para> - - <para>On the other hand, if you need to connect many drives, going - for Fast-wide SCSI may not be a bad idea. That will have the same - max bandwidth as Ultra (narrow) SCSI, while electronically it's - much easier to get it <quote>right</quote>. My advice would be: if - you want to connect many disks, get wide SCSI drives; they usually - cost a little more but it may save you down the road. (Besides, - if you can't afford the cost difference, you shouldn't be building - a disk array.)</para> - - <para>There are two variant of wide SCSI drives; 68-pin and 80-pin - SCA (Single Connector Attach). The SCA drives don't have a - separate 4-pin power connector, and also read the SCSI ID settings - through the 80-pin connector. If you are really serious about - building a large storage system, get SCA drives and a good SCA - enclosure (dual power supply with at least one extra fan). They - are more electronically sound than 68-pin counterparts because - there is no <quote>stub</quote> of the SCSI bus inside the disk - canister as in arrays built from 68-pin drives. They are easier - to install too (you just need to screw the drive in the canister, - instead of trying to squeeze in your fingers in a tight place to - hook up all the little cables (like the SCSI ID and disk activity - LED lines).</para> - </sect3> - </sect2> - - <sect2> - <title>* IDE hard drives</title> - - <para></para> - </sect2> - </sect1> - - <sect1> - <title>Tape drives</title> - - <para><emphasis>Contributed by &a.jmb;. 2 July - 1996.</emphasis></para> - - <sect2> - <title>General tape access commands</title> - - <para>&man.mt.1; provides generic access to the tape drives. Some of - the more common commands are <command>rewind</command>, - <command>erase</command>, and <command>status</command>. See the - &man.mt.1; manual page for a detailed description.</para> - </sect2> - - <sect2> - <title>Controller Interfaces</title> - - <para>There are several different interfaces that support tape drives. - The interfaces are SCSI, IDE, Floppy and Parallel Port. A wide - variety of tape drives are available for these interfaces. - Controllers are discussed in <link - linkend="hw-storage-controllers">Disk/tape - controllers</link>.</para> - </sect2> - - <sect2> - <title>SCSI drives</title> - - <para>The &man.st.4; driver provides support for 8mm (Exabyte), 4mm - (DAT: Digital Audio Tape), QIC (Quarter-Inch Cartridge), DLT - (Digital Linear Tape), QIC Mini cartridge and 9-track (remember the - big reels that you see spinning in Hollywood computer rooms) tape - drives. See the &man.st.4; manual page for a detailed - description.</para> - - <para>The drives listed below are currently being used by members of - the FreeBSD community. They are not the only drives that will work - with FreeBSD. They just happen to be the ones that we use.</para> - - <sect3> - <title>4mm (DAT: Digital Audio Tape)</title> - - <para><link linkend="hw-storage-python-28454">Archive Python - 28454</link></para> - - <para><link linkend="hw-storage-python-04687">Archive Python - 04687</link></para> - - <para><link linkend="hw-storage-hp1533a">HP C1533A</link></para> - - <para><link linkend="hw-storage-hp1534a">HP C1534A</link></para> - - <para><link linkend="hw-storage-hp35450a">HP 35450A</link></para> - - <para><link linkend="hw-storage-hp35470a">HP 35470A</link></para> - - <para><link linkend="hw-storage-hp35480a">HP 35480A</link></para> - - <para><link linkend="hw-storage-sdt5000">SDT-5000</link></para> - - <para><link linkend="hw-storage-wangtek6200">Wangtek - 6200</link></para> - </sect3> - - <sect3> - <title>8mm (Exabyte)</title> - - <para><link linkend="hw-storage-exb8200">EXB-8200</link></para> - - <para><link linkend="hw-storage-exb8500">EXB-8500</link></para> - - <para><link linkend="hw-storage-exb8505">EXB-8505</link></para> - </sect3> - - <sect3> - <title>QIC (Quarter-Inch Cartridge)</title> - - <para><link linkend="hw-storage-anaconda">Archive Anaconda - 2750</link></para> - - <para><link linkend="hw-storage-viper60">Archive Viper - 60</link></para> - - <para><link linkend="hw-storage-viper150">Archive Viper - 150</link></para> - - <para><link linkend="hw-storage-viper2525">Archive Viper - 2525</link></para> - - <para><link linkend="hw-storage-tandberg3600">Tandberg TDC - 3600</link></para> - - <para><link linkend="hw-storage-tandberg3620">Tandberg TDC - 3620</link></para> - - <para><link linkend="hw-storage-tandberg3800">Tandberg TDC - 3800</link></para> - - <para><link linkend="hw-storage-tandberg4222">Tandberg TDC - 4222</link></para> - - <para><link linkend="hw-storage-wangtek5525es">Wangtek - 5525ES</link></para> - </sect3> - - <sect3> - <title>DLT (Digital Linear Tape)</title> - - <para><link linkend="hw-storage-dectz87">Digital TZ87</link></para> - </sect3> - - <sect3> - <title>Mini-Cartridge</title> - - <para><link linkend="hw-storage-ctms3200">Conner CTMS - 3200</link></para> - - <para><link linkend="hw-storage-exb2501">Exabyte 2501</link></para> - </sect3> - - <sect3> - <title>Autoloaders/Changers</title> - - <para><link linkend="hw-storage-hp1553a">Hewlett-Packard HP C1553A - Autoloading DDS2</link></para> - </sect3> - </sect2> - - <sect2> - <title>* IDE drives</title> - - <para></para> - </sect2> - - <sect2> - <title>Floppy drives</title> - - <para><link linkend="hw-storage-conner420r">Conner 420R</link></para> - </sect2> - - <sect2> - <title>* Parallel port drives</title> - - <para></para> - </sect2> - - <sect2> - <title>Detailed Information</title> - - <sect3 id="hw-storage-anaconda"> - <title>Archive Anaconda 2750</title> - - <para>The boot message identifier for this drive is <literal>ARCHIVE - ANCDA 2750 28077 -003 type 1 removable SCSI 2</literal></para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 1.35GB when using QIC-1350 tapes. This - drive will read and write QIC-150 (DC6150), QIC-250 (DC6250), and - QIC-525 (DC6525) tapes as well.</para> - - <para>Data transfer rate is 350kB/s using &man.dump.8;. - Rates of 530kB/s have been reported when using - Amanda</para> - - <para>Production of this drive has been discontinued.</para> - - <para>The SCSI bus connector on this tape drive is reversed from - that on most other SCSI devices. Make sure that you have enough - SCSI cable to twist the cable one-half turn before and after the - Archive Anaconda tape drive, or turn your other SCSI devices - upside-down.</para> - - <para>Two kernel code changes are required to use this drive. This - drive will not work as delivered.</para> - - <para>If you have a SCSI-2 controller, short jumper 6. Otherwise, - the drive behaves are a SCSI-1 device. When operating as a SCSI-1 - device, this drive, <quote>locks</quote> the SCSI bus during some - tape operations, including: fsf, rewind, and rewoffl.</para> - - <para>If you are using the NCR SCSI controllers, patch the file - <filename>/usr/src/sys/pci/ncr.c</filename> (as shown below). - Build and install a new kernel.</para> - - <programlisting>*** 4831,4835 **** - }; - -! if (np->latetime>4) { - /* - ** Although we tried to wake it up, ---- 4831,4836 ---- - }; - -! if (np->latetime>1200) { - /* - ** Although we tried to wake it up,</programlisting> - - <para>Reported by: &a.jmb;</para> - </sect3> - - <sect3 id="hw-storage-python-28454"> - <title>Archive Python 28454</title> - - <para>The boot message identifier for this drive is <literal>ARCHIVE - Python 28454-XXX4ASB</literal> <literal>type 1 removable SCSI - 2</literal> <literal>density code 0x8c, 512-byte - blocks</literal></para> - - <para>This is a DDS-1 tape drive.</para> - - <para>Native capacity is 2.5GB on 90m tapes.</para> - - <para>Data transfer rate is XXX.</para> - - <para>This drive was repackaged by Sun Microsystems as model - 595-3067.</para> - - <para>Reported by: Bob Bishop <email>rb@gid.co.uk</email></para> - - <para>Throughput is in the 1.5 MByte/sec range, however this will - drop if the disks and tape drive are on the same SCSI - controller.</para> - - <para>Reported by: Robert E. Seastrom - <email>rs@seastrom.com</email></para> - </sect3> - - <sect3 id="hw-storage-python-04687"> - <title>Archive Python 04687</title> - - <para>The boot message identifier for this drive is <literal>ARCHIVE - Python 04687-XXX 6580</literal> <literal>Removable Sequential - Access SCSI-2 device</literal></para> - - <para>This is a DAT-DDS-2 drive.</para> - - <para>Native capacity is 4GB when using 120m tapes.</para> - - <para>This drive supports hardware data compression. Switch 4 - controls MRS (Media Recognition System). MRS tapes have stripes - on the transparent leader. Switch 4 <emphasis>off</emphasis> - enables MRS, <emphasis>on</emphasis> disables MRS.</para> - - <para>Parity is controlled by switch 5. Switch 5 - <emphasis>on</emphasis> to enable parity control. Compression is - enabled with Switch 6 <emphasis>off</emphasis>. It is possible to - override compression with the <literal>SCSI MODE SELECT</literal> - command (see &man.mt.1;).</para> - - <para>Data transfer rate is 800kB/s.</para> - </sect3> - - <sect3 id="hw-storage-viper60"> - <title>Archive Viper 60</title> - - <para>The boot message identifier for this drive is <literal>ARCHIVE - VIPER 60 21116 -007</literal> <literal>type 1 removable SCSI - 1</literal></para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 60MB.</para> - - <para>Data transfer rate is XXX.</para> - - <para>Production of this drive has been discontinued.</para> - - <para>Reported by: Philippe Regnauld - <email>regnauld@hsc.fr</email></para> - </sect3> - - <sect3 id="hw-storage-viper150"> - <title>Archive Viper 150</title> - - <para>The boot message identifier for this drive is <literal>ARCHIVE - VIPER 150 21531 -004</literal> <literal>Archive Viper 150 is a - known rogue</literal> <literal>type 1 removable SCSI - 1</literal>. A multitude of firmware revisions exist for this - drive. Your drive may report different numbers (e.g - <literal>21247 -005</literal>.</para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 150/250MB. Both 150MB (DC6150) and 250MB - (DC6250) tapes have the recording format. The 250MB tapes are - approximately 67% longer than the 150MB tapes. This drive can - read 120MB tapes as well. It can not write 120MB tapes.</para> - - <para>Data transfer rate is 100kB/s</para> - - <para>This drive reads and writes DC6150 (150MB) and DC6250 (250MB) - tapes.</para> - - <para>This drives quirks are known and pre-compiled into the scsi - tape device driver (&man.st.4;).</para> - - <para>Under FreeBSD 2.2-CURRENT, use <command>mt blocksize - 512</command> to set the blocksize. (The particular drive had - firmware revision 21247 -005. Other firmware revisions may behave - differently) Previous versions of FreeBSD did not have this - problem.</para> - - <para>Production of this drive has been discontinued.</para> - - <para>Reported by: Pedro A M Vazquez - <email>vazquez@IQM.Unicamp.BR</email></para> - - <para>&a.msmith;</para> - </sect3> - - <sect3 id="hw-storage-viper2525"> - <title>Archive Viper 2525</title> - - <para>The boot message identifier for this drive is <literal>ARCHIVE - VIPER 2525 25462 -011</literal> <literal>type 1 removable SCSI - 1</literal></para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 525MB.</para> - - <para>Data transfer rate is 180kB/s at 90 inches/sec.</para> - - <para>The drive reads QIC-525, QIC-150, QIC-120 and QIC-24 tapes. - Writes QIC-525, QIC-150, and QIC-120.</para> - - <para>Firmware revisions prior to <literal>25462 -011</literal> are - bug ridden and will not function properly.</para> - - <para>Production of this drive has been discontinued.</para> - </sect3> - - <sect3 id="hw-storage-conner420r"> - <title>Conner 420R</title> - - <para>The boot message identifier for this drive is <literal>Conner - tape</literal>.</para> - - <para>This is a floppy controller, mini cartridge tape drive.</para> - - <para>Native capacity is XXXX</para> - - <para>Data transfer rate is XXX</para> - - <para>The drive uses QIC-80 tape cartridges.</para> - - <para>Reported by: Mark Hannon - <email>mark@seeware.DIALix.oz.au</email></para> - </sect3> - - <sect3 id="hw-storage-ctms3200"> - <title>Conner CTMS 3200</title> - - <para>The boot message identifier for this drive is <literal>CONNER - CTMS 3200 7.00</literal> <literal>type 1 removable SCSI - 2</literal>.</para> - - <para>This is a mini cartridge tape drive.</para> - - <para>Native capacity is XXXX</para> - - <para>Data transfer rate is XXX</para> - - <para>The drive uses QIC-3080 tape cartridges.</para> - - <para>Reported by: Thomas S. Traylor - <email>tst@titan.cs.mci.com</email></para> - </sect3> - - <sect3 id="hw-storage-dectz87"> - <title><ulink - url="http://www.digital.com/info/Customer-Update/931206004.txt.html">DEC TZ87</ulink></title> - - <para>The boot message identifier for this drive is <literal>DEC - TZ87 (C) DEC 9206</literal> <literal>type 1 removable SCSI - 2</literal> <literal>density code 0x19</literal></para> - - <para>This is a DLT tape drive.</para> - - <para>Native capacity is 10GB.</para> - - <para>This drive supports hardware data compression.</para> - - <para>Data transfer rate is 1.2MB/s.</para> - - <para>This drive is identical to the Quantum DLT2000. The drive - firmware can be set to emulate several well-known drives, - including an Exabyte 8mm drive.</para> - - <para>Reported by: &a.wilko;</para> - </sect3> - - <sect3 id="hw-storage-exb2501"> - <title><ulink - url="http://www.Exabyte.COM:80/Products/Minicartridge/2501/Rfeatures.html">Exabyte EXB-2501</ulink></title> - - <para>The boot message identifier for this drive is <literal>EXABYTE - EXB-2501</literal></para> - - <para>This is a mini-cartridge tape drive.</para> - - <para>Native capacity is 1GB when using MC3000XL - mini cartridges.</para> - - <para>Data transfer rate is XXX</para> - - <para>This drive can read and write DC2300 (550MB), DC2750 (750MB), - MC3000 (750MB), and MC3000XL (1GB) mini cartridges.</para> - - <para>WARNING: This drive does not meet the SCSI-2 specifications. - The drive locks up completely in response to a SCSI MODE_SELECT - command unless there is a formatted tape in the drive. Before - using this drive, set the tape blocksize with</para> - - <screen>&prompt.root; <userinput>mt -f /dev/st0ctl.0 blocksize 1024</userinput></screen> - - <para>Before using a mini cartridge for the first time, the - mini cartridge must be formated. FreeBSD 2.1.0-RELEASE and - earlier:</para> - - <screen>&prompt.root; <userinput>/sbin/scsi -f /dev/rst0.ctl -s 600 -c "4 0 0 0 0 0"</userinput></screen> - - <para>(Alternatively, fetch a copy of the - <command>scsiformat</command> shell script from FreeBSD - 2.1.5/2.2.) FreeBSD 2.1.5 and later:</para> - - <screen>&prompt.root; <userinput>/sbin/scsiformat -q -w /dev/rst0.ctl</userinput></screen> - - <para>Right now, this drive cannot really be recommended for - FreeBSD.</para> - - <para>Reported by: Bob Beaulieu - <email>ez@eztravel.com</email></para> - </sect3> - - <sect3 id="hw-storage-exb8200"> - <title>Exabyte EXB-8200</title> - - <para>The boot message identifier for this drive is <literal>EXABYTE - EXB-8200 252X</literal> <literal>type 1 removable SCSI - 1</literal></para> - - <para>This is an 8mm tape drive.</para> - - <para>Native capacity is 2.3GB.</para> - - <para>Data transfer rate is 270kB/s.</para> - - <para>This drive is fairly slow in responding to the SCSI bus during - boot. A custom kernel may be required (set SCSI_DELAY to 10 - seconds).</para> - - <para>There are a large number of firmware configurations for this - drive, some have been customized to a particular vendor's - hardware. The firmware can be changed via EPROM - replacement.</para> - - <para>Production of this drive has been discontinued.</para> - - <para>Reported by: &a.msmith;</para> - </sect3> - - <sect3 id="hw-storage-exb8500"> - <title>Exabyte EXB-8500</title> - - <para>The boot message identifier for this drive is <literal>EXABYTE - EXB-8500-85Qanx0 0415</literal> <literal>type 1 removable SCSI - 2</literal></para> - - <para>This is an 8mm tape drive.</para> - - <para>Native capacity is 5GB.</para> - - <para>Data transfer rate is 300kB/s.</para> - - <para>Reported by: Greg Lehey <email>grog@lemis.de</email></para> - </sect3> - - <sect3 id="hw-storage-exb8505"> - <title><ulink - url="http://www.Exabyte.COM:80/Products/8mm/8505XL/Rfeatures.html">Exabyte EXB-8505</ulink></title> - - <para>The boot message identifier for this drive is - <literal>EXABYTE EXB-85058SQANXR1 05B0</literal> <literal>type 1 - removable SCSI 2</literal></para> - - <para>This is an 8mm tape drive which supports compression, and is - upward compatible with the EXB-5200 and EXB-8500.</para> - - <para>Native capacity is 5GB.</para> - - <para>The drive supports hardware data compression.</para> - - <para>Data transfer rate is 300kB/s.</para> - - <para>Reported by: Glen Foster - <email>gfoster@gfoster.com</email></para> - </sect3> - - <sect3 id="hw-storage-hp1533a"> - <title>Hewlett-Packard HP C1533A</title> - - <para>The boot message identifier for this drive is <literal>HP - C1533A 9503</literal> <literal>type 1 removable SCSI - 2</literal>.</para> - - <para>This is a DDS-2 tape drive. DDS-2 means hardware data - compression and narrower tracks for increased data - capacity.</para> - - <para>Native capacity is 4GB when using 120m tapes. This drive - supports hardware data compression.</para> - - <para>Data transfer rate is 510kB/s.</para> - - <para>This drive is used in Hewlett-Packard's SureStore 6000eU and - 6000i tape drives and C1533A DDS-2 DAT drive.</para> - - <para>The drive has a block of 8 dip switches. The proper settings - for FreeBSD are: 1 ON; 2 ON; 3 OFF; 4 ON; 5 ON; 6 ON; 7 ON; 8 - ON.</para> - - <informaltable frame="none"> - <tgroup cols="3"> - <thead> - <row> - <entry>switch 1</entry> - <entry>switch 2</entry> - <entry>Result</entry> - </row> - </thead> - - <tbody> - <row> - <entry>On</entry> - <entry>On</entry> - <entry>Compression enabled at power-on, with host - control</entry> - </row> - - <row> - <entry>On</entry> - <entry>Off</entry> - <entry>Compression enabled at power-on, no host - control</entry> - </row> - - <row> - <entry>Off</entry> - <entry>On</entry> - <entry>Compression disabled at power-on, with host - control</entry> - </row> - - <row> - <entry>Off</entry> - <entry>Off</entry> - <entry>Compression disabled at power-on, no host - control</entry> - </row> - </tbody> - </tgroup> - </informaltable> - - <para>Switch 3 controls MRS (Media Recognition System). MRS tapes - have stripes on the transparent leader. These identify the tape - as DDS (Digital Data Storage) grade media. Tapes that do not have - the stripes will be treated as write-protected. Switch 3 OFF - enables MRS. Switch 3 ON disables MRS.</para> - - <para>See <ulink url="http://www.hp.com/tape/c_intro.html">HP - SureStore Tape Products</ulink> and <ulink - url="http://www.impediment.com/hp/hp_technical.html">Hewlett-Packard - Disk and Tape Technical Information</ulink> for more information - on configuring this drive.</para> - - <para><emphasis>Warning:</emphasis> Quality control on these drives - varies greatly. One FreeBSD core-team member has returned 2 of - these drives. Neither lasted more than 5 months.</para> - - <para>Reported by: &a.se;</para> - </sect3> - - <sect3 id="hw-storage-hp1534a"> - <title>Hewlett-Packard HP 1534A</title> - - <para>The boot message identifier for this drive is <literal>HP - HP35470A T503</literal> <literal>type 1 removable SCSI - 2</literal> <literal>Sequential-Access density code 0x13, - variable blocks</literal>.</para> - - <para>This is a DDS-1 tape drive. DDS-1 is the original DAT tape - format.</para> - - <para>Native capacity is 2GB when using 90m tapes.</para> - - <para>Data transfer rate is 183kB/s.</para> - - <para>The same mechanism is used in Hewlett-Packard's SureStore - <ulink url="http://www.dmo.hp.com/tape/sst2000.htm">2000i</ulink> - tape drive, C35470A DDS format DAT drive, C1534A DDS format DAT - drive and HP C1536A DDS format DAT drive.</para> - - <para>The HP C1534A DDS format DAT drive has two indicator lights, - one green and one amber. The green one indicates tape action: - slow flash during load, steady when loaded, fast flash during - read/write operations. The amber one indicates warnings: slow - flash when cleaning is required or tape is nearing the end of its - useful life, steady indicates an hard fault. (factory service - required?)</para> - - <para>Reported by Gary Crutcher - <email>gcrutchr@nightflight.com</email></para> - </sect3> - - <sect3 id="hw-storage-hp1553a"> - <title>Hewlett-Packard HP C1553A Autoloading DDS2</title> - - <para>The boot message identifier for this drive is "".</para> - - <para>This is a DDS-2 tape drive with a tape changer. DDS-2 means - hardware data compression and narrower tracks for increased data - capacity.</para> - - <para>Native capacity is 24GB when using 120m tapes. This drive - supports hardware data compression.</para> - - <para>Data transfer rate is 510kB/s (native).</para> - - <para>This drive is used in Hewlett-Packard's SureStore <ulink - url="http://www.dmo.hp.com/tape/sst12000.htm">12000e</ulink> - tape drive.</para> - - <para>The drive has two selectors on the rear panel. The selector - closer to the fan is SCSI id. The other selector should be set to - 7.</para> - - <para>There are four internal switches. These should be set: 1 ON; - 2 ON; 3 ON; 4 OFF.</para> - - <para>At present the kernel drivers do not automatically change - tapes at the end of a volume. This shell script can be used to - change tapes:</para> - - <programlisting>#!/bin/sh -PATH="/sbin:/usr/sbin:/bin:/usr/bin"; export PATH - -usage() -{ - echo "Usage: dds_changer [123456ne] raw-device-name - echo "1..6 = Select cartridge" - echo "next cartridge" - echo "eject magazine" - exit 2 -} - -if [ $# -ne 2 ] ; then - usage -fi - -cdb3=0 -cdb4=0 -cdb5=0 - -case $1 in - [123456]) - cdb3=$1 - cdb4=1 - ;; - n) - ;; - e) - cdb5=0x80 - ;; - ?) - usage - ;; -esac - -scsi -f $2 -s 100 -c "1b 0 0 $cdb3 $cdb4 $cdb5"</programlisting> - </sect3> - - <sect3 id="hw-storage-hp35450a"> - <title>Hewlett-Packard HP 35450A</title> - - <para>The boot message identifier for this drive is <literal>HP - HP35450A -A C620</literal> <literal>type 1 removable SCSI - 2</literal> <literal>Sequential-Access density code - 0x13</literal></para> - - <para>This is a DDS-1 tape drive. DDS-1 is the original DAT tape - format.</para> - - <para>Native capacity is 1.2GB.</para> - - <para>Data transfer rate is 160kB/s.</para> - - <para>Reported by: Mark Thompson - <email>mark.a.thompson@pobox.com</email></para> - </sect3> - - <sect3 id="hw-storage-hp35470a"> - <title>Hewlett-Packard HP 35470A</title> - - <para>The boot message identifier for this drive is <literal>HP - HP35470A 9 09</literal> <literal>type 1 removable SCSI - 2</literal></para> - - <para>This is a DDS-1 tape drive. DDS-1 is the original DAT tape - format.</para> - - <para>Native capacity is 2GB when using 90m tapes.</para> - - <para>Data transfer rate is 183kB/s.</para> - - <para>The same mechanism is used in Hewlett-Packard's SureStore - <ulink url="http://www.dmo.hp.com/tape/sst2000.htm">2000i</ulink> - tape drive, C35470A DDS format DAT drive, C1534A DDS format DAT - drive, and HP C1536A DDS format DAT drive.</para> - - <para><emphasis>Warning:</emphasis> Quality control on these drives - varies greatly. One FreeBSD core-team member has returned 5 of - these drives. None lasted more than 9 months.</para> - - <para>Reported by: David Dawes - <email>dawes@rf900.physics.usyd.edu.au</email> (9 09)</para> - - </sect3> - - <sect3 id="hw-storage-hp35480a"> - <title>Hewlett-Packard HP 35480A</title> - - <para>The boot message identifier for this drive is <literal>HP - HP35480A 1009</literal> <literal>type 1 removable SCSI - 2</literal> <literal>Sequential-Access density code - 0x13</literal>.</para> - - <para>This is a DDS-DC tape drive. DDS-DC is DDS-1 with hardware - data compression. DDS-1 is the original DAT tape format.</para> - - <para>Native capacity is 2GB when using 90m tapes. It cannot handle - 120m tapes. This drive supports hardware data compression. - Please refer to the section on <link - linkend="hw-storage-hp1533a">HP C1533A</link> for the proper - switch settings.</para> - - <para>Data transfer rate is 183kB/s.</para> - - <para>This drive is used in Hewlett-Packard's SureStore <ulink - url="http://www.dmo.hp.com/tape/sst5000.htm">5000eU</ulink> and - <ulink url="http://www.dmo.hp.com/tape/sst5000.htm">5000i</ulink> - tape drives and C35480A DDS format DAT drive..</para> - - <para>This drive will occasionally hang during a tape eject - operation (<command>mt offline</command>). Pressing the front - panel button will eject the tape and bring the tape drive back to - life.</para> - - <para>WARNING: HP 35480-03110 only. On at least two occasions this - tape drive when used with FreeBSD 2.1.0, an IBM Server 320 and an - 2940W SCSI controller resulted in all SCSI disk partitions being - lost. The problem has not be analyzed or resolved at this - time.</para> - </sect3> - - <sect3 id="hw-storage-sdt5000"> - <title><ulink - url="http://www.sel.sony.com/SEL/ccpg/storage/tape/t5000.html">Sony SDT-5000</ulink></title> - - <para>There are at least two significantly different models: one is - a DDS-1 and the other DDS-2. The DDS-1 version is - <literal>SDT-5000 3.02</literal>. The DDS-2 version is - <literal>SONY SDT-5000 327M</literal>. The DDS-2 version has a 1MB - cache. This cache is able to keep the tape streaming in almost - any circumstances.</para> - - <para>The boot message identifier for this drive is <literal>SONY - SDT-5000 3.02</literal> <literal>type 1 removable SCSI - 2</literal> <literal>Sequential-Access density code - 0x13</literal></para> - - <para>Native capacity is 4GB when using 120m tapes. This drive - supports hardware data compression.</para> - - <para>Data transfer rate is depends upon the model or the drive. The - rate is 630kB/s for the <literal>SONY SDT-5000 327M</literal> - while compressing the data. For the <literal>SONY SDT-5000 - 3.02</literal>, the data transfer rate is 225kB/s.</para> - - <para>In order to get this drive to stream, set the blocksize to 512 - bytes (<command>mt blocksize 512</command>) reported by Kenneth - Merry <email>ken@ulc199.residence.gatech.edu</email>.</para> - - <para><literal>SONY SDT-5000 327M</literal> information reported by - Charles Henrich <email>henrich@msu.edu</email>.</para> - - <para>Reported by: &a.jmz;</para> - </sect3> - - <sect3 id="hw-storage-tandberg3600"> - <title>Tandberg TDC 3600</title> - - <para>The boot message identifier for this drive is - <literal>TANDBERG TDC 3600 =08:</literal> <literal>type 1 - removable SCSI 2</literal></para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 150/250MB.</para> - - <para>This drive has quirks which are known and work around code is - present in the scsi tape device driver (&man.st.4;). - Upgrading the firmware to XXX version will fix the quirks and - provide SCSI 2 capabilities.</para> - - <para>Data transfer rate is 80kB/s.</para> - - <para>IBM and Emerald units will not work. Replacing the firmware - EPROM of these units will solve the problem.</para> - - <para>Reported by: &a.msmith;</para> - </sect3> - - <sect3 id="hw-storage-tandberg3620"> - <title>Tandberg TDC 3620</title> - - <para>This is very similar to the <link - linkend="hw-storage-tandberg3600">Tandberg TDC 3600</link> - drive.</para> - - <para>Reported by: &a.joerg;</para> - </sect3> - - <sect3 id="hw-storage-tandberg3800"> - <title>Tandberg TDC 3800</title> - - <para>The boot message identifier for this drive is - <literal>TANDBERG TDC 3800 =04Y</literal> <literal>Removable - Sequential Access SCSI-2 device</literal></para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 525MB.</para> - - <para>Reported by: &a.jhs;</para> - </sect3> - - <sect3 id="hw-storage-tandberg4222"> - <title>Tandberg TDC 4222</title> - - <para>The boot message identifier for this drive is - <literal>TANDBERG TDC 4222 =07</literal> <literal>type 1 removable - SCSI 2</literal></para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 2.5GB. The drive will read all cartridges - from the 60 MB (DC600A) upwards, and write 150 MB (DC6150) - upwards. Hardware compression is optionally supported for the 2.5 - GB cartridges.</para> - - <para>This drives quirks are known and pre-compiled into the scsi - tape device driver (&man.st.4;) beginning with FreeBSD - 2.2-CURRENT. For previous versions of FreeBSD, use - <command>mt</command> to read one block from the tape, rewind the - tape, and then execute the backup program (<command>mt fsr 1; mt - rewind; dump ...</command>)</para> - - <para>Data transfer rate is 600kB/s (vendor claim with compression), - 350 KB/s can even be reached in start/stop mode. The rate - decreases for smaller cartridges.</para> - - <para>Reported by: &a.joerg;</para> - </sect3> - - <sect3 id="hw-storage-wangtek5525es"> - <title>Wangtek 5525ES</title> - - <para>The boot message identifier for this drive is <literal>WANGTEK - 5525ES SCSI REV7 3R1</literal> <literal>type 1 removable SCSI - 1</literal> <literal>density code 0x11, 1024-byte - blocks</literal></para> - - <para>This is a QIC tape drive.</para> - - <para>Native capacity is 525MB.</para> - - <para>Data transfer rate is 180kB/s.</para> - - <para>The drive reads 60, 120, 150, and 525MB tapes. The drive will - not write 60MB (DC600 cartridge) tapes. In order to overwrite 120 - and 150 tapes reliably, first erase (<command>mt erase</command>) - the tape. 120 and 150 tapes used a wider track (fewer tracks per - tape) than 525MB tapes. The <quote>extra</quote> width of the - previous tracks is not overwritten, as a result the new data lies - in a band surrounded on both sides by the previous data unless the - tape have been erased.</para> - - <para>This drives quirks are known and pre-compiled into the scsi - tape device driver (&man.st.4;).</para> - - <para>Other firmware revisions that are known to work are: - M75D</para> - - <para>Reported by: Marc van Kempen <email>marc@bowtie.nl</email> - <literal>REV73R1</literal> Andrew Gordon - <email>Andrew.Gordon@net-tel.co.uk</email> - <literal>M75D</literal></para> - </sect3> - - <sect3 id="hw-storage-wangtek6200"> - <title>Wangtek 6200</title> - - <para>The boot message identifier for this drive is <literal>WANGTEK - 6200-HS 4B18</literal> <literal>type 1 removable SCSI - 2</literal> <literal>Sequential-Access density code - 0x13</literal></para> - - <para>This is a DDS-1 tape drive.</para> - - <para>Native capacity is 2GB using 90m tapes.</para> - - <para>Data transfer rate is 150kB/s.</para> - - <para>Reported by: Tony Kimball <email>alk@Think.COM</email></para> - </sect3> - </sect2> - - <sect2> - <title>* Problem drives</title> - - <para></para> - </sect2> - </sect1> - - <sect1> - <title>CDROM drives</title> - - <para><emphasis>Contributed by &a.obrien;. 23 November - 1997.</emphasis></para> - - <para>Generally speaking those in <emphasis>The FreeBSD - Project</emphasis> prefer SCSI CDROM drives over IDE CDROM - drives. However not all SCSI CDROM drives are equal. Some - feel the quality of some SCSI CDROM drives have been - deteriorating to that of IDE CDROM drives. Toshiba used to be - the favored stand-by, but many on the SCSI mailing list have - found displeasure with the 12x speed XM-5701TA as its volume - (when playing audio CDROMs) is not controllable by the various - audio player software.</para> - - <para>Another area where SCSI CDROM manufacturers are cutting corners is - adherence to the <link linkend="scsi-further-reading">SCSI - specification</link>. Many SCSI CDROMs will respond to <link - linkend="scsi-rogue-devices">multiple LUNs</link> for its target - address. Known violators include the 6x Teac CD-56S 1.0D.</para> - </sect1> - -</article>
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