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CTL(4)		       FreeBSD Kernel Interfaces Manual			CTL(4)

     ctl -- CAM	Target Layer

     To	compile	this driver into the kernel, place the following line in your
     kernel configuration file:

	   device ctl

     Alternatively, to load the	driver as a module at boot time, place the
     following line in loader.conf(5):


     The ctl subsystem provides	SCSI target devices emulation.	It supports
     features such as:

     +o	 Disk, CD-ROM and processor device emulation
     +o	 Tagged	queueing
     +o	 SCSI task attribute support (ordered, head of queue, simple tags)
     +o	 SCSI implicit command ordering	support
     +o	 Full task management support (abort, query, reset, etc.)
     +o	 Support for multiple ports, initiators, targets and backing stores
     +o	 Support for VMWare VAAI and Microsoft ODX offload (COMPARE AND	WRITE,
     +o	 Persistent reservation	support
     +o	 Extensive VPD/mode/log	pages support
     +o	 Featured error	reporting, error injection and basic SMART support
     +o	 High Availability clustering support with ALUA
     +o	 All I/O handled in-kernel, no userland	context	switch overhead

     The ctl subsystem includes	multiple frontends to provide access using
     different transport protocols and implementations:

     camsim   Provides access for local	system via virtual initiator mode
	      CAM(4) SIM.

     camtgt   Provides access for remote systems via target mode CAM(4)	SIMs,
	      such as Fibre Channel isp(4) and mpt(4).

     cfumass  Provides access for remote systems via USB Mass Storage Class
	      Bulk Only	(BBB) Transport.

     ha	      Internal frontend	used to	receive	requests from other node ports
	      in High Availability cluster.

     ioctl    Provides access for local	user-level applications	via ioctl(2)
	      based API.

     iscsi    Provides access for remote systems via the iSCSI protocol	using

     tpc      Internal frontend	used to	receive	requests from Third Party Copy
	      engine, implementing copy	offload	operations.

     The ctl subsystem includes	two backends to	create logical units using
     different kinds of	backing	stores:

     block    Stores data in ZFS ZVOLs,	files or raw block devices.

     ramdisk  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.

     The following variables are available as both sysctl(8) variables and
     loader(8) tunables:
	     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.
	     Specifies unique position of this node within High	Availability
	     cluster.  Default is 0 -- no HA, 1	and 2 -- HA enabled at speci-
	     fied position.
	     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	for-
			   wards 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 re-
	     port Unavailable state; if	configured but not established --
	     Transitioning state.  Defaults to 0.
	     String value, specifying method to	establish connection to	peer
	     HA	node.  Can be "listen IP:port",	"connect IP:port" or empty.
	     Reports present state of connection between HA cluster nodes:
		   0	   not configured;
		   1	   configured but not established;
		   2	   established.
	     Specifies default role of this node:
		   0	   primary;
		   1	   secondary.
	     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	an-
	     other -- 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).

     The following variables are available as loader(8)	tunables:
	     Specifies the maximum number of LUNs we support, must be a	power
	     of	2.  The	default	value is 1024.
	     Specifies the maximum number of ports we support, must be a power
	     of	2.  The	default	value is 256.

     cfiscsi(4), cfumass(4), ctladm(8),	ctld(8), ctlstat(8)

     The ctl subsystem first appeared in FreeBSD 9.1.

     The ctl subsystem was originally written by Kenneth Merry
     <>.	 Later work was	done by
     Alexander Motin <>.

FreeBSD	13.0			March 29, 2017			  FreeBSD 13.0


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