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Add a kern.nvmf.fail_on_disconnection sysctl similar to the kern.iscsi.fail_on_disconnection sysctl. This causes pending I/O requests to fail with an error if an association is disconnected instead of requeueing to be retried once the association is reconnected. As with iSCSI, the default is to queue and retry operations. Reviewed by: imp Sponsored by: Chelsio Communications Differential Revision: https://reviews.freebsd.org/D45308
110 lines
2.6 KiB
Groff
110 lines
2.6 KiB
Groff
.\"
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.\" SPDX-License-Identifier: BSD-2-Clause
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.\"
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.\" Copyright (c) 2024 Chelsio Communications, Inc.
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.\"
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.Dd June 5, 2024
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.Dt NVMF 4
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.Os
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.Sh NAME
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.Nm nvmf
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.Nd "NVM Express over Fabrics host driver"
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.Sh SYNOPSIS
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To compile the driver into the kernel,
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place the following line in the
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device nvmf"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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nvmf_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides the kernel component of an NVM Express over Fabrics
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host.
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The NVMeoF host is the client which provides local access to
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namespaces exported by a remote controller.
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.Pp
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Associations between the local host and remote controllers are managed
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using
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.Xr nvmecontrol 8 .
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New associations are created via the
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.Cm connect
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command and destroyed via the
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.Cm disconnect
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command.
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If an association's connection is interrupted,
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the
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.Cm reconnect
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command creates a new association to replace the interrupted association.
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.Pp
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Similar to
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.Xr nvme 4 ,
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.Nm
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creates controller device nodes using the format
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.Pa /dev/nvmeX
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and namespace device nodes using the format
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.Pa /dev/nvmeXnsY .
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.Nm
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also exports remote namespaces via the CAM
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.Xr nda 4
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peripheral driver.
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Unlike
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.Xr nvme 4 ,
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.Nm
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does not support the
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.Xr nvd 4
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disk driver.
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.Pp
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Associations require a supported transport such as
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.Xr nvmf_tcp 4
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for associations using TCP/IP.
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.Sh SYSCTL VARIABLES
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The following variables are available as both
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.Xr sysctl 8
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variables and
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.Xr loader 8
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tunables:
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.Bl -tag -width indent
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.It Va kern.nvmf.fail_on_disconnection
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Determines the behavior when an association's connection is interrupted.
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By default, input/output operations are suspended while a host is disconnected.
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This includes operations pending at the time the association's connection was
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interrupted as well as new requests submitted while the host is disconnected.
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Once a new association is established, suspended I/O requests are retried.
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When set to 1, input/output operations fail with
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.Er EIO
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while a host is disconnected and
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.Xr nda 4
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peripherals are destroyed after the first failed I/O request.
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Note that any destroyed
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.Xr nda 4
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peripherals will be recreated after a new association is established.
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.El
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.Sh SEE ALSO
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.Xr nda 4 ,
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.Xr nvme 4 ,
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.Xr nvmf_tcp 4 ,
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.Xr nvmft 4 ,
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.Xr nvmecontrol 8
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.Sh HISTORY
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The
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.Nm
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module first appeared in
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.Fx 15.0 .
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.Sh AUTHORS
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The
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.Nm
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driver was developed by
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.An John Baldwin Aq Mt jhb@FreeBSD.org
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under sponsorship from Chelsio Communications, Inc.
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.Sh BUGS
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.Nm
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only supports a single I/O queue pair per association.
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