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diff --git a/website/content/en/status/report-2023-04-2023-06/nvmf.adoc b/website/content/en/status/report-2023-04-2023-06/nvmf.adoc new file mode 100644 index 0000000000..f9477918e4 --- /dev/null +++ b/website/content/en/status/report-2023-04-2023-06/nvmf.adoc @@ -0,0 +1,40 @@ +=== NVMe over Fabrics + +Links: + +link:https://github.com/bsdjhb/freebsd/tree/nvmf2[nvmf2 branch] URL: link:https://github.com/bsdjhb/freebsd/tree/nvmf2[] + +Contact: John Baldwin <jhb@FreeBSD.org> + +NVMe over Fabrics enables communication with a storage device using the NVMe protocol over a network fabric. +This is similar to using iSCSI to export a storage device over a network using SCSI commands. + +NVMe over Fabrics currently defines network transports for Fibre Channel, RDMA, and TCP. + +The work in the nvmf2 branch includes a userland library ([.filename]#lib/libnvmf#) which contains an abstraction for transports and an implementation of +a TCP transport. +It also includes changes to man:nvmecontrol[8] to add 'discover', 'connect', and 'disconnect' commands to manage connections to a remote controller. + +The branch also contains an in-kernel Fabrics implementation. +[.filename]#nvmf_transport.ko# contains a transport abstraction that sits in between the nvmf host (initiator in SCSI terms) and the individual transports. +[.filename]#nvmf_tcp.ko# contains an implementation of the TCP transport layer. +[.filename]#nvmf.ko# contains an NVMe over Fabrics host (initiator) which connects to a remote controller and exports remote namespaces as disk devices. +Similar to the man:nvme[4] driver for NVMe over PCI-express, namespaces are exported via [.filename]#/dev/nvmeXnsY# devices which only support simple operations, but are also exported as ndaX disk devices via CAM. +Unlike man:nvme[4], man:nvmf[4] does not support the man:nvd[4] disk driver. +man:nvmecontrol[8] can be used with remote namespaces and remote controllers, for example to fetch log pages, display identify info, etc. + +Note that man:nvmf[4] is currently a bit simple and some error cases are still a TODO. +If an error occurs, the queues (and backing network connections) are dropped, but the devices stay around, with I/O requests paused. +`nvmecontrol reconnect` can be used to connect a new set of network connections to resume operation. +Unlike iSCSI which uses a persistent daemon (man:iscsid[8]) to reconnect after an error, reconnections must be made manually. + +The current code is very new and likely not robust. +It is certainly not ready for production use. +Experienced users who do not mind all their data vanishing in a puff of smoke after a kernel panic, and who have an interest in NVMe over Fabrics, can start testing it at their own risk. + +The next main task is to implement a Fabrics controller (target in SCSI language). +Probably a simple one in userland first followed by a "real" one that offloads the data handling to the kernel but is somewhat integrated with man:ctld[8] so that individual disk devices can be exported via iSCSI or NVMe, or via both using a single config file and daemon to manage all of that. +This may require a fair bit of refactoring in ctld to make it less iSCSI-specific. +Working on the controller side will also validate some of the currently under-tested API design decisions in the transport-independent layer. +I think it probably does not make sense to merge any of the NVMe over Fabrics changes into the tree until after this step. + +Sponsored by: Chelsio Communications |