ctl(4freebsd)
NAME
ctl --- CAM Target Layer / iSCSI target
SYNOPSIS
To compile this driver into the kernel, place the following line in your
kernel configuration file:
device iscsi
device ctl
Alternatively, to load the driver as a module at boot time, place the
following line in loader.conf(5):
ctl_load="YES"
DESCRIPTION
The ctl subsystem provides SCSI disk and processor emulation. It
supports features such as:
* Disk, processor and cdrom device emulation
* Tagged queueing
* SCSI task attribute support (ordered, head of queue, simple tags)
* SCSI implicit command ordering support
* Full task management support (abort, LUN reset, target reset, etc.)
* Support for multiple ports
* Support for multiple simultaneous initiators
* Support for multiple simultaneous backing stores
* Support for VMWare VAAI: COMPARE AND WRITE, XCOPY, WRITE SAME, and
UNMAP commands
* Support for Microsoft ODX: POPULATE TOKEN/WRITE USING TOKEN, WRITE
SAME, and UNMAP commands
* Persistent reservation support
* Mode sense/select support
* Error injection support
* High Availability clustering support with ALUA
* All I/O handled in-kernel, no userland context switch overhead
It also serves as a kernel component of the native iSCSI target.
SYSCTL VARIABLES
The following variables are available as both sysctl(8) variables and
loader(8) tunables:
kern.cam.ctl.debug
Bit mask of enabled CTL log levels:
1 log commands with errors;
2 log all commands;
4 log data for commands other then READ/WRITE.
Defaults to 0.
kern.cam.ctl.ha_id
Specifies unique position of this node within High Availability
cluster. Default is 0 -- no HA, 1 and 2 -- HA enabled at
specified position.
kern.cam.ctl.ha_mode
Specifies High Availability cluster operation mode:
0 Active/Standby -- primary node has backend
access and processes requests, while
secondary can only do basic LUN discovery and
reservation;
1 Active/Active -- both nodes have backend
access and process requests, while secondary
node synchronizes processing with primary
one;
2 Active/Active -- primary node has backend
access and processes requests, while
secondary node forwards all requests and data
to primary one;
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.
kern.cam.ctl.ha_peer
String value, specifying method to establish connection to peer
HA node. Can be "listen IP:port", "connect IP:port" or empty.
kern.cam.ctl.ha_link
Reports present state of connection between HA cluster nodes:
0 not configured;
1 configured but not established;
2 established.
kern.cam.ctl.ha_role
Specifies default role of this node:
0 primary;
1 secondary.
This role can be overriden 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).
kern.cam.ctl.iscsi.debug
Verbosity level for log messages from the kernel part of iSCSI
target. Set to 0 to disable logging or 1 to warn about potential
problems. Larger values enable debugging output. Defaults to 1.
kern.cam.ctl.iscsi.maxcmdsn_delta
The number of outstanding commands to advertise to the iSCSI
initiator. Technically, it is the difference between ExpCmdSN
and MaxCmdSN fields in the iSCSI PDU. Defaults to 256.
kern.cam.ctl.iscsi.ping_timeout
The number of seconds to wait for the iSCSI initiator to respond
to a NOP-In PDU. In the event that there is no response within
that time the session gets forcibly terminated. Set to 0 to
disable sending NOP-In PDUs. Defaults to 5.
SEE ALSO
ctladm(8), ctld(8), ctlstat(8)
HISTORY
The ctl subsystem first appeared in FreeBSD 9.1.
AUTHORS
The ctl subsystem was originally written by Kenneth Merry
[email protected]. Later work was done by
Alexander Motin [email protected].
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