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Improve ctl(4) description, including frontends and backends.

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Alexander Motin 2017-03-11 20:23:05 +00:00
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share/man/man4/ctl.4
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@ -1,5 +1,5 @@
.\" Copyright (c) 2013 Edward Tomasz Napierala
.\" Copyright (c) 2015 Alexander Motin <mav@FreeBSD.org>
.\" Copyright (c) 2015-2017 Alexander Motin <mav@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
@ -24,15 +24,14 @@
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD$
.Dd January 19, 2017
.Dd March 11, 2017
.Dt CTL 4
.Os
.Sh NAME
.Nm ctl
.Nd CAM Target Layer / iSCSI target
.Nd CAM Target Layer / SCSI target subsystem
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
To compile this driver into the kernel, place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device iscsi"
@ -48,45 +47,87 @@ ctl_load="YES"
.Sh DESCRIPTION
The
.Nm
subsystem provides SCSI disk and processor emulation.
subsystem provides featured, performant and reliable SCSI target devices
emulation.
It supports features such as:
.Pp
.Bl -bullet -compact
.It
Disk, processor and cdrom device emulation
.It
Tagged queueing
Tagged and untagged queueing
.It
SCSI task attribute support (ordered, head of queue, simple tags)
.It
SCSI implicit command ordering support
.It
Full task management support (abort, LUN reset, target reset, etc.)
Full task management support (abort, query, reset, etc.)
.It
Support for multiple ports
Support for multiple ports, initiators, targets and backing stores
.It
Support for multiple simultaneous initiators
.It
Support for multiple simultaneous backing stores
.It
Support for VMWare VAAI: COMPARE AND WRITE, XCOPY, WRITE SAME,
and UNMAP commands
.It
Support for Microsoft ODX: POPULATE TOKEN/WRITE USING TOKEN,
WRITE SAME, and UNMAP commands
Support for VMWare VAAI and Microsoft ODX offload (COMPARE AND WRITE,
XCOPY, POPULATE TOKEN/WRITE USING TOKEN, WRITE SAME and UNMAP)
.It
Persistent reservation support
.It
Mode sense/select support
Extensive VPD/mode/log pages support
.It
Error injection support
Featured error reporting, error injection and basic SMART support
.It
High Availability clustering support with ALUA
.It
All I/O handled in-kernel, no userland context switch overhead
.El
.Pp
It also serves as a kernel component of the native iSCSI target.
The
.Nm
subsystem includes multiple frontends to provide access using different
transport protocols and implementations:
.Bl -tag -width cfumass
.It camsim
Provides access for local system via virtual initiator mode
.Xr CAM 4
SIM.
.It camtgt
Provides access for remote systems via target mode
.Xr CAM 4
SIMs, such as Fibre Channel
.Xr isp 4
and
.Xr mpt 4 .
.It cfumass
Provides access for remote systems via USB Mass Storage Class
Bulk Only (BBB) Transport.
.It ha
Internal frontend used to receive requests from other node ports in
High Availability cluster.
.It ioctl
Provides access for local user-level applications via
.Xr ioctl 2
based API.
.It iscsi
Combined with
.Xr iscsi 4
and
.Xr ctld 8 ,
provides access for remote systems via iSCSI protocol.
.It tpc
Internal frontend used to receive requests from Third Party Copy engine,
implementing copy offload operations.
.El
.Pp
The
.Nm
subsystem includes two backends to create logical units using different
kinds of backing stores:
.Bl -tag -width ramdisk
.It block
Stores data on ZFS ZVOLs, files or raw block devices.
.It 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.
.El
.Sh SYSCTL VARIABLES
The following variables are available as both
.Xr sysctl 8