git: 4222032e43 - main - Status/2023Q2/nvmf.adoc: Improvements
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Date: Wed, 12 Jul 2023 16:35:41 UTC
The branch main has been updated by salvadore: URL: https://cgit.FreeBSD.org/doc/commit/?id=4222032e43c581f284023b917dff5dc3ade0e874 commit 4222032e43c581f284023b917dff5dc3ade0e874 Author: Lorenzo Salvadore <salvadore@FreeBSD.org> AuthorDate: 2023-07-12 16:28:25 +0000 Commit: Lorenzo Salvadore <salvadore@FreeBSD.org> CommitDate: 2023-07-12 16:28:25 +0000 Status/2023Q2/nvmf.adoc: Improvements - Switch to one sentence per line. - Add one more use of the filename markup. Approved by: dbaio (mentor, implicit) --- .../en/status/report-2023-04-2023-06/nvmf.adoc | 75 +++++++--------------- 1 file changed, 22 insertions(+), 53 deletions(-) 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 index 445119c7f9..a9ceefdaea 100644 --- a/website/content/en/status/report-2023-04-2023-06/nvmf.adoc +++ b/website/content/en/status/report-2023-04-2023-06/nvmf.adoc @@ -5,67 +5,36 @@ link:https://github.com/bsdjhb/freebsd/tree/nvmf2[nvmf2 branch] URL: link:https: 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 enables communication with a storage device usingthe 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. +NVMe over Fabrics currently defines network transports for Fibre Channel, RDMA, and TCP. -The work in the nvmf2 branch includes a userland library (lib/libnvmf) -which contains an abstraction for transports and an implementation of +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. +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. -nvmecontrol 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, but 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 done manually. +[.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. +nvmecontrol 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, but 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 done 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. +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 -either via iSCSI or NVMe or 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. +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 either via iSCSI or NVMe or 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. 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