1 .\" Copyright (c) 2013 Edward Tomasz Napierala
2 .\" Copyright (c) 2015 Alexander Motin <mav@FreeBSD.org>
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27 .Dd September 27, 2015
32 .Nd CAM Target Layer / iSCSI target
34 To compile this driver into the kernel,
35 place the following line in your
36 kernel configuration file:
37 .Bd -ragged -offset indent
42 Alternatively, to load the driver as a
43 module at boot time, place the following line in
45 .Bd -literal -offset indent
51 subsystem provides SCSI disk and processor emulation.
52 It supports features such as:
56 Disk, processor and cdrom device emulation
60 SCSI task attribute support (ordered, head of queue, simple tags)
62 SCSI implicit command ordering support
64 Full task management support (abort, LUN reset, target reset, etc.)
66 Support for multiple ports
68 Support for multiple simultaneous initiators
70 Support for multiple simultaneous backing stores
72 Support for VMWare VAAI: COMPARE AND WRITE, XCOPY, WRITE SAME,
75 Support for Microsoft ODX: POPULATE TOKEN/WRITE USING TOKEN,
76 WRITE SAME, and UNMAP commands
78 Persistent reservation support
80 Mode sense/select support
82 Error injection support
84 High Availability clustering support with ALUA
86 All I/O handled in-kernel, no userland context switch overhead
89 It also serves as a kernel component of the native iSCSI target.
91 The following variables are available as both
96 .Bl -tag -width indent
97 .It Va kern.cam.ctl.debug
98 Bit mask of enabled CTL log levels:
99 .Bl -tag -offset indent -compact
101 log commands with errors;
105 log data for commands other then READ/WRITE.
108 .It Va kern.cam.ctl.ha_id
109 Specifies unique position of this node within High Availability cluster.
110 Default is 0 -- no HA, 1 and 2 -- HA enabled at specified position.
111 .It Va kern.cam.ctl.ha_mode
112 Specifies High Availability cluster operation mode:
113 .Bl -tag -offset indent -compact
115 Active/Standby -- primary node has backend access and processes requests,
116 while secondary can only do basic LUN discovery and reservation;
118 Active/Active -- both nodes have backend access and process requests,
119 while secondary node synchronizes processing with primary one;
121 Active/Active -- primary node has backend access and processes requests,
122 while secondary node forwards all requests and data to primary one;
124 All above modes require established connection between HA cluster nodes.
125 If connection is not configured, secondary node will report Unavailable
126 state; if configured but not established -- Transitioning state.
128 .It Va kern.cam.ctl.ha_peer
129 String value, specifying method to establish connection to peer HA node.
130 Can be "listen IP:port", "connect IP:port" or empty.
131 .It Va kern.cam.ctl.ha_link
132 Reports present state of connection between HA cluster nodes:
133 .Bl -tag -offset indent -compact
137 configured but not established;
141 .It Va kern.cam.ctl.ha_role
142 Specifies default role of this node:
143 .Bl -tag -offset indent -compact
149 This role can be overriden on per-LUN basis using "ha_role" LUN option,
150 so that for one LUN one node is primary, while for another -- another.
151 Role change from primary to secondary for HA modes 0 and 2 closes backends,
152 the opposite change -- opens.
153 If there is no primary node (both nodes are secondary, or secondary node has
154 no connection to primary one), secondary node(s) report Transitioning state.
155 State with two primary nodes is illegal (split brain condition).
156 .It Va kern.cam.ctl.iscsi.debug
157 Verbosity level for log messages from the kernel part of iSCSI target.
158 Set to 0 to disable logging or 1 to warn about potential problems.
159 Larger values enable debugging output.
161 .It Va kern.cam.ctl.iscsi.maxcmdsn_delta
162 The number of outstanding commands to advertise to the iSCSI initiator.
163 Technically, it is the difference between ExpCmdSN and MaxCmdSN fields
166 .It Va kern.cam.ctl.iscsi.ping_timeout
167 The number of seconds to wait for the iSCSI initiator to respond to a NOP-In
169 In the event that there is no response within that time the session gets
171 Set to 0 to disable sending NOP-In PDUs.
181 subsystem first appeared in
186 subsystem was originally written by
187 .An Kenneth Merry Aq Mt ken@FreeBSD.org .
188 Later work was done by
189 .An Alexander Motin Aq Mt mav@FreeBSD.org .