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

     ctl -- CAM	Target Layer / iSCSI target

     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):


     The ctl subsystem provides	SCSI disk and processor	emulation.  It sup-
     ports features such as:

     +o	 Disk, processor and cdrom 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, LUN reset, target	reset, etc.)
     +o	 Support for multiple ports
     +o	 Support for multiple simultaneous initiators
     +o	 Support for multiple simultaneous backing stores
     +o	 Support for VMWare VAAI: COMPARE AND WRITE, XCOPY, WRITE SAME,	and
	 UNMAP commands
	 SAME, and UNMAP commands
     +o	 Persistent reservation	support
     +o	 Mode sense/select support
     +o	 Error injection support
     +o	 High Availability clustering support with ALUA
     +o	 All I/O handled in-kernel, no userland	context	switch overhead

     It	also serves as a kernel	component of the native	iSCSI target.

     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 sec-
				 ondary	can only do basic LUN discovery	and
		   1		 Active/Active -- both nodes have backend
				 access	and process requests, while secondary
				 node synchronizes processing with primary
		   2		 Active/Active -- primary node has backend
				 access	and processes requests,	while sec-
				 ondary	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.
	     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 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).
	     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.
	     The number	of outstanding commands	to advertise to	the iSCSI ini-
	     tiator.  Technically, it is the difference	between	ExpCmdSN and
	     MaxCmdSN fields in	the iSCSI PDU.	Defaults to 256.
	     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 dis-
	     able sending NOP-In PDUs.	Defaults to 5.

     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	11.0		      September	27, 2015		  FreeBSD 11.0


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