3 CTL - CAM Target Layer Description
5 Revision 1.4 (December 29th, 2011)
6 Ken Merry <ken@FreeBSD.org>
13 Configuring and Running CTL
22 CTL is a disk, processor and cdrom device emulation subsystem originally
23 written for Copan Systems under Linux starting in 2003. It has been
24 shipping in Copan (now SGI) products since 2005.
26 It was ported to FreeBSD in 2008, and thanks to an agreement between SGI
27 (who acquired Copan's assets in 2010) and Spectra Logic in 2010, CTL is
28 available under a BSD-style license. The intent behind the agreement was
29 that Spectra would work to get CTL into the FreeBSD tree.
34 - Disk, processor and cdrom device emulation.
36 - SCSI task attribute support (ordered, head of queue, simple tags)
37 - SCSI implicit command ordering support. (e.g. if a read follows a mode
38 select, the read will be blocked until the mode select completes.)
39 - Full task management support (abort, LUN reset, target reset, etc.)
40 - Support for multiple ports
41 - Support for multiple simultaneous initiators
42 - Support for multiple simultaneous backing stores
43 - Support for VMWare VAAI: COMPARE AND WRITE, XCOPY, WRITE SAME and
45 - Support for Microsoft ODX: POPULATE TOKEN/WRITE USING TOKEN, WRITE SAME
47 - Persistent reservation support
48 - Mode sense/select support
49 - Error injection support
50 - High Availability clustering support with ALUA
51 - All I/O handled in-kernel, no userland context switch overhead.
53 Configuring and Running CTL:
54 ===========================
56 - Add 'device ctl' to your kernel configuration file or load the module.
58 - If you're running with a 8Gb or 4Gb Qlogic FC board, add
59 'options ISP_TARGET_MODE' to your kernel config file. 'device ispfw' or
60 loading the ispfw module is also recommended.
62 - Rebuild and install a new kernel.
64 - Reboot with the new kernel.
66 - To add a LUN with the RAM disk backend:
68 ctladm create -b ramdisk -s 10485760000000000000
71 - You should now see the CTL disk LUN through camcontrol devlist:
73 scbus6 on ctl2cam0 bus 0:
74 <FREEBSD CTLDISK 0001> at scbus6 target 1 lun 0 (da24,pass32)
75 <> at scbus6 target -1 lun -1 ()
77 This is visible through the CTL CAM SIM. This allows using CTL without
78 any physical hardware. You should be able to issue any normal SCSI
79 commands to the device via the pass(4)/da(4) devices.
81 If any target-capable HBAs are in the system (e.g. isp(4)), and have
82 target mode enabled, you should now also be able to see the CTL LUNs via
83 that target interface.
85 Note that all CTL LUNs are presented to all frontends. There is no
86 LUN masking, or separate, per-port configuration.
88 - Note that the ramdisk backend is a "fake" ramdisk. That is, it is
89 backed by a small amount of RAM that is used for all I/O requests. This
90 is useful for performance testing, but not for any data integrity tests.
92 - To add a LUN with the block/file backend:
94 truncate -s +1T myfile
95 ctladm create -b block -o file=myfile
98 - You can also see a list of LUNs and their backends like this:
101 LUN Backend Size (Blocks) BS Serial Number Device ID
102 0 block 2147483648 512 MYSERIAL 0 MYDEVID 0
103 1 block 2147483648 512 MYSERIAL 1 MYDEVID 1
104 2 block 2147483648 512 MYSERIAL 2 MYDEVID 2
105 3 block 2147483648 512 MYSERIAL 3 MYDEVID 3
106 4 block 2147483648 512 MYSERIAL 4 MYDEVID 4
107 5 block 2147483648 512 MYSERIAL 5 MYDEVID 5
108 6 block 2147483648 512 MYSERIAL 6 MYDEVID 6
109 7 block 2147483648 512 MYSERIAL 7 MYDEVID 7
110 8 block 2147483648 512 MYSERIAL 8 MYDEVID 8
111 9 block 2147483648 512 MYSERIAL 9 MYDEVID 9
112 10 block 2147483648 512 MYSERIAL 10 MYDEVID 10
113 11 block 2147483648 512 MYSERIAL 11 MYDEVID 11
115 - You can see the LUN type and backing store for block/file backend LUNs
119 LUN Backend Size (Blocks) BS Serial Number Device ID
120 0 block 2147483648 512 MYSERIAL 0 MYDEVID 0
124 1 block 2147483648 512 MYSERIAL 1 MYDEVID 1
128 2 block 2147483648 512 MYSERIAL 2 MYDEVID 2
132 3 block 2147483648 512 MYSERIAL 3 MYDEVID 3
136 4 block 2147483648 512 MYSERIAL 4 MYDEVID 4
140 5 block 2147483648 512 MYSERIAL 5 MYDEVID 5
144 6 block 2147483648 512 MYSERIAL 6 MYDEVID 6
148 7 block 2147483648 512 MYSERIAL 7 MYDEVID 7
152 8 block 2147483648 512 MYSERIAL 8 MYDEVID 8
156 9 block 2147483648 512 MYSERIAL 9 MYDEVID 9
160 10 ramdisk 0 0 MYSERIAL 0 MYDEVID 0
162 11 ramdisk 204800000000000 512 MYSERIAL 1 MYDEVID 1
167 - Added in the second HA mode (where CTL does the data transfers instead
168 of having data transfers done below CTL), and abstracted out the Copan
171 - Fixed the phantom device problem in the CTL CAM SIM and improved the
172 CAM SIM to automatically trigger a rescan when the port is enabled and
175 - Made the number of threads in the block backend configurable via sysctl,
176 loader tunable and the ctladm command line. (You can now specify
177 -o num_threads=4 when creating a LUN with ctladm create.)
179 - Fixed some LUN selection issues in ctlstat(8) and allowed for selection
180 of LUN numbers up to 1023.
184 - This version intended for public release.
188 - Added descriptor sense support to CTL. It can be enabled through the
189 control mode page (10), but is disabled by default.
191 - Improved error injection support. The number of errors that can be
192 injected with 'ctladm inject' has been increased, and any arbitrary
193 sense data may now be injected as well.
195 - The port infrastructure has been revamped. Individual ports and types
196 of ports may now be enabled and disabled from the command line. ctladm
197 now has the ability to set the WWNN and WWPN for each port.
199 - The block backend can now send multiple I/Os to backing files. Multiple
200 writes are only allowed for ZFS, but multiple readers are allowed for
203 - The block and ramdisk backends now support setting the LUN blocksize.
204 There are some restrictions when the backing device is a block device,
205 but otherwise the blocksize may be set to anything.
210 - CTL initialization process has been revamped. Instead of using an
211 ad-hoc method, it is now sequenced through SYSINIT() calls.
213 - A block/file backend has been added. This allows using arbitrary files
214 or block devices as a backing store.
216 - The userland LUN configuration interface has been completely rewritten.
217 Configuration is now done out of band.
219 - The ctladm(8) command line interface has been revamped, and is now
220 similar to camcontrol(8).
225 - Use devstat(9) for CTL's statistics collection. CTL uses a home-grown
226 statistics collection system that is similar to devstat(9). ctlstat
227 should be retired in favor of iostat, etc., once aggregation modes are
228 available in iostat to match the behavior of ctlstat -t and dump modes
229 are available to match the behavior of ctlstat -d/ctlstat -J.
231 - ZFS ARC backend for CTL. Since ZFS copies all I/O into the ARC
232 (Adaptive Replacement Cache), running the block/file backend on top of a
233 ZFS-backed zdev or file will involve an extra set of copies. The
234 optimal solution for backing targets served by CTL with ZFS would be to
235 allocate buffers out of the ARC directly, and DMA to/from them directly.
236 That would eliminate an extra data buffer allocation and copy.
238 - Switch CTL over to using CAM CCBs instead of its own union ctl_io. This
239 will likely require a significant amount of work, but will eliminate
240 another data structure in the stack, more memory allocations, etc. This
241 will also require changes to the CAM CCB structure to support CTL.
246 CTL has the concept of pluggable frontend ports and backends. All
247 frontends and backends can be active at the same time. You can have a
248 ramdisk-backed LUN present along side a file backed LUN.
253 This is the core of CTL, where all of the command handlers and a lot of
254 other things live. Yes, it is large. It started off small and grew to its
255 current size over time. Perhaps it can be split into more files at some
258 Here is a roadmap of some of the primary functions in ctl.c. Starting here
259 and following the various leaf functions will show the command flow.
261 ctl_queue() / ctl_run() This is where commands from the frontend ports come
264 ctl_queue_sense() This is only used for non-packetized SCSI. i.e.
265 parallel SCSI prior to U320 and perhaps U160.
267 ctl_work_thread() This is the primary work thread, and everything gets
270 ctl_scsiio_precheck() This where all of the initial checks are done, and I/O
271 is either queued for execution or blocked.
273 ctl_scsiio() This is where the command handler is actually
274 executed. (See ctl_cmd_table.c for the mapping of
275 SCSI opcode to command handler function.)
277 ctl_done() This is the routine called (or ctl_done_lock()) to
278 initiate the command completion process.
280 ctl_process_done() This is where command completion actually happens.
285 Basic function declarations and data structures.
291 These files define the basic CTL backend API. The comments in the header
297 The block and file backend. This allows for using a disk or a file as the
298 backing store for a LUN. Multiple threads are started to do I/O to the
299 backing device, primarily because the VFS API requires that to get any
302 ctl_backend_ramdisk.c:
303 ---------------------
305 A "fake" ramdisk backend. It only allocates a small amount of memory to
306 act as a source and sink for reads and writes from an initiator. Therefore
307 it cannot be used for any real data, but it can be used to test for
308 throughput. It can also be used to test initiators' support for extremely
314 This is a table with all 256 possible SCSI opcodes, and command handler
315 functions defined for supported opcodes. It is included in ctl.c.
320 Simplistic debugging support.
326 CTL-specific wrappers around the CAM sense building functions.
332 These files define the basic CTL frontend port API. The comments in the
333 header explain the API.
335 ctl_frontend_cam_sim.c:
336 ----------------------
338 This is a CTL frontend port that is also a CAM SIM. The idea is that this
339 frontend allows for using CTL without any target-capable hardware. So any
340 LUNs you create in CTL are visible via this port.
346 This is a High Availability API and TCP-based interlink implementation.
351 This defines most of the core CTL I/O structures. union ctl_io is
352 conceptually very similar to CAM's union ccb.
357 This defines all ioctls available through the CTL character device, and
358 the data structures needed for those ioctls.
363 Private data structres (e.g. CTL softc) and function prototypes. This also
364 includes the SCSI vendor and product names used by CTL.
370 CTL wrappers around CAM sense printing functions.
375 Command serialization table. This defines what happens when one type of
376 command is followed by another type of command. e.g., what do you do when
377 you have a mode select followed by a write? You block the write until the
378 mode select is complete. That is defined in this table.
384 CTL utility functions, primarily designed to be used from userland. See
385 ctladm for the primary consumer of these functions. These include CDB
391 CAM target peripheral driver and CTL frontend port. This is the path into
392 CTL for commands from target-capable hardware/SIMs.
397 ctladm(8) fills a role similar to camcontrol(8). It allow configuring LUNs,
398 issuing commands, injecting errors and various other control functions.
400 ctlstat(8) fills a role similar to iostat(8). It reports I/O statistics