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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
     supports 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
     +o   Support for Microsoft ODX: POPULATE TOKEN/WRITE USING TOKEN, WRITE
         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
             specified 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 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
             initiator.  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
             disable 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-PRERELEASE       September 27, 2015       FreeBSD 11.0-PRERELEASE


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