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<table class="head">
<tr>
<td class="head-ltitle">CTL(4)</td>
<td class="head-vol">Device Drivers Manual</td>
<td class="head-rtitle">CTL(4)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">ctl</code> — <span class="Nd">CAM Target
Layer</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="SYNOPSIS"><a class="permalink" href="#SYNOPSIS">SYNOPSIS</a></h1>
<p class="Pp">To compile this driver into the kernel, place the following line
in your kernel configuration file:</p>
<div class="Bd Pp Bd-indent"><code class="Cd">device ctl</code></div>
<p class="Pp">Alternatively, to load the driver as a module at boot time, place
the following line in <a class="Xr">loader.conf(5)</a>:</p>
<div class="Bd Pp Bd-indent Li">
<pre>ctl_load="YES"</pre>
</div>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The <code class="Nm">ctl</code> subsystem provides SCSI target
devices emulation. It supports features such as:</p>
<p class="Pp"></p>
<ul class="Bl-bullet Bl-compact">
<li>Disk, CD-ROM and processor device emulation</li>
<li>Tagged queueing</li>
<li>SCSI task attribute support (ordered, head of queue, simple tags)</li>
<li>SCSI implicit command ordering support</li>
<li>Full task management support (abort, query, reset, etc.)</li>
<li>Support for multiple ports, initiators, targets and backing stores</li>
<li>Support for VMWare VAAI and Microsoft ODX offload (COMPARE AND WRITE,
XCOPY, POPULATE TOKEN/WRITE USING TOKEN, WRITE SAME and UNMAP)</li>
<li>Persistent reservation support</li>
<li>Extensive VPD/mode/log pages support</li>
<li>Featured error reporting, error injection and basic SMART support</li>
<li>High Availability clustering support with ALUA</li>
<li>All I/O handled in-kernel, no userland context switch overhead</li>
</ul>
<p class="Pp">The <code class="Nm">ctl</code> subsystem includes multiple
frontends to provide access using different transport protocols and
implementations:</p>
<dl class="Bl-tag">
<dt>camsim</dt>
<dd>Provides access for local system via virtual initiator mode
<a class="Xr">CAM(4)</a> SIM.</dd>
<dt>camtgt</dt>
<dd>Provides access for remote systems via target mode
<a class="Xr">CAM(4)</a> SIMs, such as Fibre Channel
<a class="Xr">isp(4)</a> and <a class="Xr">mpt(4)</a>.</dd>
<dt>cfumass</dt>
<dd>Provides access for remote systems via USB Mass Storage Class Bulk Only
(BBB) Transport.</dd>
<dt>ha</dt>
<dd>Internal frontend used to receive requests from other node ports in High
Availability cluster.</dd>
<dt>ioctl</dt>
<dd>Provides access for local user-level applications via
<a class="Xr">ioctl(2)</a> based API.</dd>
<dt>iscsi</dt>
<dd>Provides access for remote systems via the iSCSI protocol using
<a class="Xr">cfiscsi(4)</a>.</dd>
<dt>tpc</dt>
<dd>Internal frontend used to receive requests from Third Party Copy engine,
implementing copy offload operations.</dd>
</dl>
<p class="Pp">The <code class="Nm">ctl</code> subsystem includes two backends to
create logical units using different kinds of backing stores:</p>
<dl class="Bl-tag">
<dt>block</dt>
<dd>Stores data in ZFS ZVOLs, files or raw block devices.</dd>
<dt>ramdisk</dt>
<dd>Stores data in RAM, that makes it mostly useful for performance testing.
Depending on configured capacity can work as black hole, thin or thick
provisioned disk.</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SYSCTL_VARIABLES"><a class="permalink" href="#SYSCTL_VARIABLES">SYSCTL
VARIABLES</a></h1>
<p class="Pp">The following variables are available as both
<a class="Xr">sysctl(8)</a> variables and <a class="Xr">loader(8)</a>
tunables:</p>
<dl class="Bl-tag">
<dt id="kern.cam.ctl.debug"><var class="Va">kern.cam.ctl.debug</var></dt>
<dd>Bit mask of enabled CTL log levels:
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt>1</dt>
<dd>log commands with errors;</dd>
<dt>2</dt>
<dd>log all commands;</dd>
<dt>4</dt>
<dd>log data for commands other then READ/WRITE.</dd>
</dl>
</div>
Defaults to 0.</dd>
<dt id="kern.cam.ctl.ha_id"><var class="Va">kern.cam.ctl.ha_id</var></dt>
<dd>Specifies unique position of this node within High Availability cluster.
Default is 0 -- no HA, 1 and 2 -- HA enabled at specified position.</dd>
<dt id="kern.cam.ctl.ha_mode"><var class="Va">kern.cam.ctl.ha_mode</var></dt>
<dd>Specifies High Availability cluster operation mode:
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt>0</dt>
<dd>Active/Standby -- primary node has backend access and processes
requests, while secondary can only do basic LUN discovery and
reservation;</dd>
<dt>1</dt>
<dd>Active/Active -- both nodes have backend access and process requests,
while secondary node synchronizes processing with primary one;</dd>
<dt>2</dt>
<dd>Active/Active -- primary node has backend access and processes
requests, while secondary node forwards all requests and data to
primary one;</dd>
</dl>
</div>
All above modes require established connection between HA cluster nodes. If
connection is not configured, secondary node will report Unavailable
state; if configured but not established -- Transitioning state. Defaults
to 0.</dd>
<dt id="kern.cam.ctl.ha_peer"><var class="Va">kern.cam.ctl.ha_peer</var></dt>
<dd>String value, specifying method to establish connection to peer HA node.
Can be "listen IP:port", "connect IP:port" or
empty.</dd>
<dt id="kern.cam.ctl.ha_link"><var class="Va">kern.cam.ctl.ha_link</var></dt>
<dd>Reports present state of connection between HA cluster nodes:
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt>0</dt>
<dd>not configured;</dd>
<dt>1</dt>
<dd>configured but not established;</dd>
<dt>2</dt>
<dd>established.</dd>
</dl>
</div>
</dd>
<dt id="kern.cam.ctl.ha_role"><var class="Va">kern.cam.ctl.ha_role</var></dt>
<dd>Specifies default role of this node:
<div class="Bd-indent">
<dl class="Bl-tag Bl-compact">
<dt>0</dt>
<dd>primary;</dd>
<dt>1</dt>
<dd>secondary.</dd>
</dl>
</div>
This role can be overridden on per-LUN basis using "ha_role" LUN
option, so that for one LUN one node is primary, while for another --
another. Role change from primary to secondary for HA modes 0 and 2 closes
backends, the opposite change -- opens. If there is no primary node (both
nodes are secondary, or secondary node has no connection to primary one),
secondary node(s) report Transitioning state. State with two primary nodes
is illegal (split brain condition).</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="TUNABLE_VARIABLES"><a class="permalink" href="#TUNABLE_VARIABLES">TUNABLE
VARIABLES</a></h1>
<p class="Pp">The following variables are available as
<a class="Xr">loader(8)</a> tunables:</p>
<dl class="Bl-tag">
<dt id="kern.cam.ctl.max_luns"><var class="Va">kern.cam.ctl.max_luns</var></dt>
<dd>Specifies the maximum number of LUNs we support, must be a power of 2. The
default value is 1024.</dd>
<dt id="kern.cam.ctl.max_ports"><var class="Va">kern.cam.ctl.max_ports</var></dt>
<dd>Specifies the maximum number of ports we support, must be a power of 2.
The default value is 1024.</dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">cfiscsi(4)</a>, <a class="Xr">cfumass(4)</a>,
<a class="Xr">ctladm(8)</a>, <a class="Xr">ctld(8)</a>,
<a class="Xr">ctlstat(8)</a></p>
</section>
<section class="Sh">
<h1 class="Sh" id="HISTORY"><a class="permalink" href="#HISTORY">HISTORY</a></h1>
<p class="Pp">The <code class="Nm">ctl</code> subsystem first appeared in
<span class="Ux">FreeBSD 9.1</span>.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="AUTHORS"><a class="permalink" href="#AUTHORS">AUTHORS</a></h1>
<p class="Pp">The <code class="Nm">ctl</code> subsystem was originally written
by <span class="An">Kenneth Merry</span>
<<a class="Mt" href="mailto:ken@FreeBSD.org">ken@FreeBSD.org</a>>.
Later work was done by
<br/>
<span class="An">Alexander Motin</span>
<<a class="Mt" href="mailto:mav@FreeBSD.org">mav@FreeBSD.org</a>>.</p>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">March 29, 2017</td>
<td class="foot-os">FreeBSD 15.0</td>
</tr>
</table>
|
