NAME

     ctl — CAM Target Layer

SYNOPSIS

     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):

           ctl_load="YES"

DESCRIPTION

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

     •   Disk, CD-ROM and processor device emulation
     •   Tagged queueing
     •   SCSI task attribute support (ordered, head of queue, simple tags)
     •   SCSI implicit command ordering support
     •   Full task management support (abort, query, reset, etc.)
     •   Support for multiple ports, initiators, targets and backing stores
     •   Support for VMWare VAAI and Microsoft ODX offload (COMPARE AND WRITE, XCOPY, POPULATE
         TOKEN/WRITE USING TOKEN, WRITE SAME and UNMAP)
     •   Persistent reservation support
     •   Extensive VPD/mode/log pages support
     •   Featured error reporting, error injection and basic SMART support
     •   High Availability clustering support with ALUA
     •   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 cfiscsi(4).

     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.

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 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).

SEE ALSO

     cfiscsi(4), cfumass(4), 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 <ken@FreeBSD.org>.  Later work was
     done by
     Alexander Motin <mav@FreeBSD.org>.