path: root/pl_PL.ISO8859-2/books/handbook/geom/chapter.xml

<?xml version="1.0" encoding="iso-8859-2"?>
<!--
     The FreeBSD Documentation Project
     $FreeBSD$

-->

<chapter id="GEOM">
  <chapterinfo>
    <authorgroup>
      <author>
	<firstname>Tom</firstname>
	<surname>Rhodes</surname>
	<contrib>Written by </contrib>
      </author>
    </authorgroup>
  </chapterinfo>

  <title>GEOM: Modular Disk Transformation Framework</title>

  <sect1 id="GEOM-synopsis">
    <title>Synopsis</title>

    <indexterm>
      <primary>GEOM</primary>
    </indexterm>
    <indexterm>
      <primary>GEOM Disk Framework</primary>
      <see>GEOM</see>
    </indexterm>

    <para>This chapter covers the use of disks under the GEOM
      framework in &os;.  This includes the major <acronym
      role="Redundant Array of Inexpensive Disks">RAID</acronym>
      control utilities which use the framework for configuration.
      This chapter will not go into in depth discussion on how GEOM
      handles or controls I/O, the underlying subsystem, or code.
      This information is provided through the &man.geom.4; manual
      page and its various SEE ALSO references.  This chapter is also
      not a definitive guide to <acronym>RAID</acronym>
      configurations.  Only GEOM-supported <acronym>RAID</acronym>
      classifications will be discussed.</para>

    <para>After reading this chapter, you will know:</para>

    <itemizedlist>
      <listitem>
	<para>What type of <acronym>RAID</acronym> support is available
	  through GEOM.</para>
      </listitem>

      <listitem>
	<para>How to use the base utilities to configure, maintain,
	  and manipulate the various <acronym>RAID</acronym>
	  levels.</para>
      </listitem>

      <listitem>
        <para>How to mirror, stripe, encrypt, and remotely connect disk
	  devices through GEOM.</para>
      </listitem>

      <listitem>
	<para>How to troubleshoot disks attached to the GEOM
	  framework.</para>
      </listitem>
    </itemizedlist>

    <para>Before reading this chapter, you should:</para>

    <itemizedlist>
      <listitem>
	<para>Understand how &os; treats disk devices
	  (<xref linkend="disks"/>).</para>
      </listitem>

      <listitem>
	<para>Know how to configure and install a new &os; kernel
	  (<xref linkend="kernelconfig"/>).</para>
      </listitem>
    </itemizedlist>
  </sect1>

  <sect1 id="GEOM-intro">
    <title>GEOM Introduction</title>

    <para>GEOM permits access and control to classes &mdash; Master Boot
      Records, <acronym>BSD</acronym> labels, etc &mdash; through the
      use of providers, or the special files in
      <filename class="directory">/dev</filename>.  Supporting various
      software <acronym>RAID</acronym> configurations, GEOM will
      transparently provide access to the operating system and
      operating system utilities.</para>
  </sect1>

  <sect1 id="GEOM-striping">
  <sect1info>
    <authorgroup>
      <author>
	<firstname>Tom</firstname>
	<surname>Rhodes</surname>
	<contrib>Written by </contrib>
      </author>
      <author>
	<firstname>Murray</firstname>
	<surname>Stokely</surname>
      </author>
    </authorgroup>
  </sect1info>

    <title>RAID0 - Striping</title>

    <indexterm>
      <primary>GEOM</primary>
    </indexterm>
    <indexterm>
      <primary>Striping</primary>
    </indexterm>

    <para>Striping is a method used to combine several disk drives into
      a single volume.  In many cases, this is done through the use of
      hardware controllers.  The GEOM disk subsystem provides
      software support for <acronym>RAID</acronym>0, also known as
      disk striping.</para>

    <para>In a <acronym>RAID</acronym>0 system, data are split up in
      blocks that get written across all the drives in the array.
      Instead of having to wait on the system to write 256k to one
      disk, a <acronym>RAID</acronym>0 system can simultaneously write
      64k to each of four different disks, offering superior I/O
      performance.  This performance can be enhanced further by using
      multiple disk controllers.</para>

    <para>Each disk in a <acronym>RAID</acronym>0 stripe must be of
      the same size, since I/O requests are interleaved to read or
      write to multiple disks in parallel.</para>

      <mediaobject>
        <imageobject>
          <imagedata fileref="geom/striping" align="center"/>
        </imageobject>

        <textobject>
          <phrase>Disk Striping Illustration</phrase>
        </textobject>
      </mediaobject>

    <procedure>
      <title>Creating a stripe of unformatted ATA disks</title>

      <step><para>Load the <filename>geom_stripe</filename>
        module:</para>

    <screen>&prompt.root; <userinput>kldload geom_stripe.ko</userinput></screen>
	</step>

      <step><para>Ensure that a suitable mount point exists.  If this
        volume will become a root partition, then temporarily use
        another mount point such as <filename
        class="directory">/mnt</filename>:</para>

        <screen>&prompt.root; <userinput>mkdir /mnt</userinput></screen>
      </step>

      <step><para>Determine the device names for the disks which will
        be striped, and create the new stripe device.  For example,
        the following command could be used to stripe two unused,
        unpartitioned <acronym>ATA</acronym> disks:
        <filename>/dev/ad2</filename> and
        <filename>/dev/ad3</filename>.</para>

        <screen>&prompt.root; <userinput>gstripe label -v st0 /dev/ad2 /dev/ad3</userinput></screen>

<!--
    <para>A message should be returned explaining that meta data has
      been stored on the devices.
XXX: What message?  Put it inside the screen output above.
-->
      </step>

      <step><para>A partition table must be created on the new volume
        with the following command:</para>

        <screen>&prompt.root; <userinput>bsdlabel -wB /dev/stripe/st0</userinput></screen>

      </step>

      <step><para>This process should have created two other devices
        in the <filename class="directory">/dev/stripe</filename>
        directory in addition to the <devicename>st0</devicename> device.
        Those include <devicename>st0a</devicename> and
        <devicename>st0c</devicename>.  A file system must now be created
        on the <devicename>st0a</devicename> device using the following
        <command>newfs</command> command:</para>

      <screen>&prompt.root; <userinput>newfs -U /dev/stripe/st0a</userinput></screen>

      <para>Many numbers will glide across the screen, and after a few
        seconds, the process will be complete.  The volume has been
        created and is ready to be mounted.</para>
    </step>
  </procedure>

  <para>The following command can be used to manually mount a newly
    created disk stripe:</para>

  <screen>&prompt.root; <userinput>mount /dev/stripe/st0a /mnt</userinput></screen>

  <para>To mount this striped file system automatically during the boot
    process, place the volume information in
    <filename>/etc/fstab</filename> file:</para>

  <screen>&prompt.root; <userinput>echo "/dev/stripe/st0a /mnt ufs rw 2 2" \</userinput>
    <userinput>&gt;&gt; /etc/fstab</userinput></screen>

  <para>The <filename>geom_stripe</filename> module must also be automatically loaded during
    system initialization, by adding a line to
    <filename>/boot/loader.conf</filename>:</para>

  <screen>&prompt.root; <userinput>echo 'geom_stripe_load="YES"' &gt;&gt; /boot/loader.conf</userinput></screen>

  </sect1>

  <sect1 id="GEOM-mirror">
    <title>RAID1 - Mirroring</title>

    <indexterm>
      <primary>GEOM</primary>
    </indexterm>
    <indexterm>
      <primary>Disk Mirroring</primary>
    </indexterm>

    <para>Mirroring is a technology used by many corporations and home
      users to back up data without interruption.  When a mirror exists,
      it simply means that diskB replicates diskA.  Or, perhaps diskC+D
      replicates diskA+B.  Regardless of the disk configuration, the
      important aspect is that information on one disk or partition is
      being replicated.  Later, that information could be more easily
      restored, backed up without causing service or access
      interruption, and even be physically stored in a data
      safe.</para>

    <para>To begin, ensure the system has two disk drives of equal size,
      this exercise assumes they are direct access (&man.da.4;)
      <acronym>SCSI</acronym> disks.</para>

    <para>Begin by installing &os; on the first disk with only two
      partitions.  One should be a swap partition, double the
      <acronym>RAM</acronym> size and all remaining space devoted to
      the root (<filename class="directory">/</filename>) file system.
      It is possible to have separate partitions for other mount points;
      however, this will increase the difficulty level ten fold due to
      manual alteration of the &man.bsdlabel.8; and &man.fdisk.8;
      settings.</para>

    <para>Reboot and wait for the system to fully initialize.  Once this
      process has completed, log in as the <username>root</username>
      user.</para>

    <para>Create the <filename>/dev/mirror/gm</filename> device and link
      it with <filename>/dev/da1</filename>:</para>

    <screen>&prompt.root; <userinput>gmirror label -vnb round-robin gm0 /dev/da1</userinput></screen>

    <para>The system should respond with:</para>
    <screen>
Metadata value stored on /dev/da1.
Done.</screen>

    <para>Initialize GEOM, this will load the
      <filename>/boot/kernel/geom_mirror.ko</filename> kernel
      module:</para>

    <screen>&prompt.root; <userinput>gmirror load</userinput></screen>

    <note>
      <para>This command should have created the
	<devicename>gm0</devicename>, device node under the
	<filename class="directory">/dev/mirror</filename>
	directory.</para>
    </note>

    <para>Install a generic <command>fdisk</command> label and boot code
      to newly created <devicename>gm0</devicename> device:</para>

    <screen>&prompt.root; <userinput>fdisk -vBI /dev/mirror/gm0</userinput></screen>

    <para>Now install generic <command>bsdlabel</command>
      information:</para>

    <screen>&prompt.root; <userinput>bsdlabel -wB /dev/mirror/gm0s1</userinput></screen>

    <note>
      <para>If multiple slices and partitions exist, the flags for the
	previous two commands will require alteration.  They must match
	the slice and partition size of the other disk.</para>
    </note>

    <para>Use the &man.newfs.8; utility to create a default file
      system on the <devicename>gm0s1a</devicename> device node:</para>

    <screen>&prompt.root; <userinput>newfs -U /dev/mirror/gm0s1a</userinput></screen>

    <para>This should have caused the system to spit out some
      information and a bunch of numbers.  This is good.  Examine the
      screen for any error messages and mount the device to the
      <filename class="directory">/mnt</filename> mount point:</para>

    <screen>&prompt.root; <userinput>mount /dev/mirror/gm0s1a /mnt</userinput></screen>

    <para>Now move all data from the boot disk over to this new file
      system.  This example uses the &man.dump.8; and &man.restore.8;
      commands; however, &man.dd.1; would also work with this
      scenario.</para>

    <screen>&prompt.root; <userinput>dump -L -0 -f- / |(cd /mnt &amp;&amp; restore -r -v -f-)</userinput></screen>

    <para>This must be done for each file system.  Simply place the
      appropriate file system in the correct location when running the
      aforementioned command.</para>

    <para>Now edit the replicated <filename>/mnt/etc/fstab</filename>
      file and remove or comment out the swap file
      <footnote>
	<para>It should be noted that commenting out the swap file entry
	in <filename>fstab</filename> will most likely require you to
	re-establish a different way of enabling swap space.  Please
	refer to <xref linkend="adding-swap-space"/> for more
	information.</para>
      </footnote>.  Change the other file system information to use the
      new disk.  See the following example:</para>

    <programlisting># Device                Mountpoint      FStype  Options         Dump    Pass#
#/dev/da0s2b             none            swap    sw              0       0
/dev/mirror/gm0s1a       /               ufs     rw              1       1</programlisting>

    <para>Now create a <filename>boot.conf</filename> file on both the
      current and new root partitions.  This file will
      <quote>help</quote> the system <acronym>BIOS</acronym>
      boot the correct drive:</para>

    <screen>&prompt.root; <userinput>echo "1:da(1,a)/boot/loader" &gt; /boot.config</userinput></screen>

    <screen>&prompt.root; <userinput>echo "1:da(1,a)/boot/loader" &gt; /mnt/boot.config</userinput></screen>

    <note>
      <para>We have placed it on both root partitions to ensure proper
        boot up.  If for some reason the system cannot read from the
	new root partition, a failsafe is available.</para>
    </note>

    <para>Now add the following line to the new
      <filename>/boot/loader.conf</filename>:</para>

    <screen>&prompt.root; <userinput>echo 'geom_mirror_load="YES"' &gt;&gt; /mnt/boot/loader.conf</userinput></screen>

    <para>This will instruct &man.loader.8; utility to load the
      <filename>geom_mirror.ko</filename> module during system
      initialization.</para>

    <para>Reboot the system:</para>

    <screen>&prompt.root; <userinput>shutdown -r now</userinput></screen>

    <para>If all has gone well, the system should have booted from the
      <devicename>gm0s1a</devicename> device and a <command>login</command>
      prompt should be waiting.  If something went wrong, see review
      the forthcoming troubleshooting section.  Now add the
      <devicename>da0</devicename> disk to <devicename>gm0</devicename>
      device:</para>

    <screen>&prompt.root; <userinput>gmirror configure -a gm0</userinput>
&prompt.root; <userinput>gmirror insert gm0 /dev/da0</userinput></screen>

    <para>The <option>-a</option> flag tells &man.gmirror.8; to use
      automatic synchronization; i.e., mirror the disk writes
      automatically.  The manual page explains how to rebuild and
      replace disks, although it uses <devicename>data</devicename>
      in place of <devicename>gm0</devicename>.</para>

    <sect2>
      <title>Troubleshooting</title>

      <sect3>
	<title>System refuses to boot</title>

	<para>If the system boots up to a prompt similar to:</para>

	<programlisting>ffs_mountroot: can't find rootvp
Root mount failed: 6
mountroot></programlisting>

	<para>Reboot the machine using the power or reset button.  At
	  the boot menu, select option six (6).  This will drop the
	  system to a &man.loader.8; prompt.  Load the kernel module
	  manually:</para>

	<screen>OK? <userinput>load geom_mirror.ko</userinput>
OK? <userinput>boot</userinput></screen>

	<para>If this works then for whatever reason the module was not
	  being loaded properly.  Place:</para>

	<programlisting>options	GEOM_MIRROR</programlisting>

	<para>in the kernel configuration file, rebuild and reinstall.
	  That should remedy this issue.</para>
      </sect3>
    </sect2>
  </sect1>

  <sect1 id="geom-ggate">
    <title>GEOM Gate Network Devices</title>

    <para>GEOM supports the remote use of devices, such as disks,
      CD-ROMs, files, etc. through the use of the gate utilities.
      This is similar to <acronym>NFS</acronym>.</para>

    <para>To begin, an exports file must be created.  This file
      specifies who is permitted to access the exported resources and
      what level of access they are offered.  For example, to export
      the forth slice on the first <acronym>SCSI</acronym> disk, the
      following <filename>/etc/gg.exports</filename> is more than
      adequate:</para>

    <programlisting>192.168.1.0/24 RW /dev/da0s4d</programlisting>

    <para>It will allow all hosts inside the private network access
      the file system on the <devicename>da0s4d</devicename>
      partition.</para>

    <para>To export this device, ensure it is not currently mounted,
      and start the &man.ggated.8; server daemon:</para>

    <screen>&prompt.root; <userinput>ggated</userinput></screen>

    <para>Now to <command>mount</command> the device on the client
      machine, issue the following commands:</para>

    <screen>&prompt.root; <userinput>ggatec create -o rw 192.168.1.1 /dev/da0s4d</userinput></screen>
    <screen>ggate0</screen>
    <screen>&prompt.root; <userinput>mount /dev/ggate0 /mnt</userinput></screen>

    <para>From here on, the device may be accessed through the
      <filename class="directory">/mnt</filename> mount point.</para>

    <note>
      <para>It should be pointed out that this will fail if the device
	is currently mounted on either the server machine or any other
	machine on the network.</para>
    </note>

    <para>When the device is no longer needed, it may be safely
      unmounted with the &man.umount.8; command, similar to any other
      disk device.</para>
  </sect1>
</chapter>