223 lines
6.7 KiB
Groff
223 lines
6.7 KiB
Groff
.\" Copyright (c) 2013 Edward Tomasz Napierala
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.\" Copyright (c) 2015-2017 Alexander Motin <mav@FreeBSD.org>
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.Dd March 29, 2017
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.Dt CTL 4
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.Os
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.Sh NAME
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.Nm ctl
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.Nd CAM Target Layer
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following line in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "device ctl"
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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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ctl_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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subsystem provides SCSI target devices emulation.
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It supports features such as:
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.Pp
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.Bl -bullet -compact
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.It
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Disk, CD-ROM and processor device emulation
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.It
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Tagged queueing
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.It
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SCSI task attribute support (ordered, head of queue, simple tags)
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.It
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SCSI implicit command ordering support
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.It
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Full task management support (abort, query, reset, etc.)
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.It
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Support for multiple ports, initiators, targets and backing stores
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.It
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Support for VMWare VAAI and Microsoft ODX offload (COMPARE AND WRITE,
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XCOPY, POPULATE TOKEN/WRITE USING TOKEN, WRITE SAME and UNMAP)
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.It
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Persistent reservation support
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.It
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Extensive VPD/mode/log pages support
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.It
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Featured error reporting, error injection and basic SMART support
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.It
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High Availability clustering support with ALUA
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.It
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All I/O handled in-kernel, no userland context switch overhead
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.El
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.Pp
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The
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.Nm
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subsystem includes multiple frontends to provide access using different
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transport protocols and implementations:
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.Bl -tag -width cfumass
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.It camsim
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Provides access for local system via virtual initiator mode
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.Xr CAM 4
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SIM.
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.It camtgt
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Provides access for remote systems via target mode
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.Xr CAM 4
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SIMs, such as Fibre Channel
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.Xr isp 4
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and
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.Xr mpt 4 .
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.It cfumass
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Provides access for remote systems via USB Mass Storage Class
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Bulk Only (BBB) Transport.
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.It ha
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Internal frontend used to receive requests from other node ports in
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High Availability cluster.
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.It ioctl
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Provides access for local user-level applications via
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.Xr ioctl 2
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based API.
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.It iscsi
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Provides access for remote systems via the iSCSI protocol using
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.Xr cfiscsi 4 .
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.It tpc
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Internal frontend used to receive requests from Third Party Copy engine,
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implementing copy offload operations.
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.El
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.Pp
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The
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.Nm
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subsystem includes two backends to create logical units using different
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kinds of backing stores:
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.Bl -tag -width ramdisk
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.It block
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Stores data in ZFS ZVOLs, files or raw block devices.
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.It ramdisk
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Stores data in RAM, that makes it mostly useful for performance testing.
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Depending on configured capacity can work as black hole, thin or thick
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provisioned disk.
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.El
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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.cam.ctl.debug
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Bit mask of enabled CTL log levels:
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.Bl -tag -offset indent -compact
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.It 1
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log commands with errors;
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.It 2
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log all commands;
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.It 4
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log data for commands other then READ/WRITE.
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.El
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Defaults to 0.
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.It Va kern.cam.ctl.ha_id
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Specifies unique position of this node within High Availability cluster.
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Default is 0 -- no HA, 1 and 2 -- HA enabled at specified position.
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.It Va kern.cam.ctl.ha_mode
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Specifies High Availability cluster operation mode:
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.Bl -tag -offset indent -compact
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.It 0
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Active/Standby -- primary node has backend access and processes requests,
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while secondary can only do basic LUN discovery and reservation;
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.It 1
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Active/Active -- both nodes have backend access and process requests,
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while secondary node synchronizes processing with primary one;
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.It 2
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Active/Active -- primary node has backend access and processes requests,
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while secondary node forwards all requests and data to primary one;
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.El
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All above modes require established connection between HA cluster nodes.
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If connection is not configured, secondary node will report Unavailable
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state; if configured but not established -- Transitioning state.
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Defaults to 0.
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.It Va kern.cam.ctl.ha_peer
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String value, specifying method to establish connection to peer HA node.
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Can be "listen IP:port", "connect IP:port" or empty.
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.It Va kern.cam.ctl.ha_link
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Reports present state of connection between HA cluster nodes:
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.Bl -tag -offset indent -compact
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.It 0
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not configured;
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.It 1
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configured but not established;
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.It 2
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established.
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.El
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.It Va kern.cam.ctl.ha_role
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Specifies default role of this node:
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.Bl -tag -offset indent -compact
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.It 0
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primary;
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.It 1
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secondary.
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.El
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This role can be overridden on per-LUN basis using "ha_role" LUN option,
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so that for one LUN one node is primary, while for another -- another.
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Role change from primary to secondary for HA modes 0 and 2 closes backends,
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the opposite change -- opens.
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If there is no primary node (both nodes are secondary, or secondary node has
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no connection to primary one), secondary node(s) report Transitioning state.
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State with two primary nodes is illegal (split brain condition).
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.El
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.Sh TUNABLE VARIABLES
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The following variables are available as
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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.cam.ctl.max_luns
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Specifies the maximum number of LUNs we support, must be a power of 2.
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The default value is 1024.
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.It Va kern.cam.ctl.max_ports
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Specifies the maximum number of ports we support, must be a power of 2.
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The default value is 256.
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.Sh SEE ALSO
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.Xr cfiscsi 4 ,
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.Xr cfumass 4 ,
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.Xr ctladm 8 ,
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.Xr ctld 8 ,
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.Xr ctlstat 8
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.Sh HISTORY
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The
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.Nm
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subsystem first appeared in
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.Fx 9.1 .
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.Sh AUTHORS
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The
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.Nm
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subsystem was originally written by
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.An Kenneth Merry Aq Mt ken@FreeBSD.org .
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Later work was done by
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.An Alexander Motin Aq Mt mav@FreeBSD.org .
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