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 and processor device emulation subsystem originally written
23 for Copan Systems under Linux starting in 2003. It has been shipping in
24 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 and processor 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 - Persistent reservation support
44 - Mode sense/select support
45 - Error injection support
46 - High Availability support
47 - All I/O handled in-kernel, no userland context switch overhead.
49 Configuring and Running CTL:
50 ===========================
52 - After applying the CTL patchset to your tree, build world and install it
53 on your target system.
55 - Add 'device ctl' to your kernel configuration file.
57 - If you're running with a 8Gb or 4Gb Qlogic FC board, add
58 'options ISP_TARGET_MODE' to your kernel config file. Keep in mind that
59 the isp(4) driver can run in target or initiator mode, but not both on
60 the same machine. 'device ispfw' or loading the ispfw module is also
63 - Rebuild and install a new kernel.
65 - Reboot with the new kernel.
67 - To add a LUN with the RAM disk backend:
69 ctladm create -b ramdisk -s 10485760000000000000
72 - You should now see the CTL disk LUN through camcontrol devlist:
74 scbus6 on ctl2cam0 bus 0:
75 <FREEBSD CTLDISK 0001> at scbus6 target 1 lun 0 (da24,pass32)
76 <> at scbus6 target -1 lun -1 ()
78 This is visible through the CTL CAM SIM. This allows using CTL without
79 any physical hardware. You should be able to issue any normal SCSI
80 commands to the device via the pass(4)/da(4) devices.
82 If any target-capable HBAs are in the system (e.g. isp(4)), and have
83 target mode enabled, you should now also be able to see the CTL LUNs via
84 that target interface.
86 Note that all CTL LUNs are presented to all frontends. There is no
87 LUN masking, or separate, per-port configuration.
89 - Note that the ramdisk backend is a "fake" ramdisk. That is, it is
90 backed by a small amount of RAM that is used for all I/O requests. This
91 is useful for performance testing, but not for any data integrity tests.
93 - To add a LUN with the block/file backend:
95 truncate -s +1T myfile
96 ctladm create -b block -o file=myfile
99 - You can also see a list of LUNs and their backends like this:
102 LUN Backend Size (Blocks) BS Serial Number Device ID
103 0 block 2147483648 512 MYSERIAL 0 MYDEVID 0
104 1 block 2147483648 512 MYSERIAL 1 MYDEVID 1
105 2 block 2147483648 512 MYSERIAL 2 MYDEVID 2
106 3 block 2147483648 512 MYSERIAL 3 MYDEVID 3
107 4 block 2147483648 512 MYSERIAL 4 MYDEVID 4
108 5 block 2147483648 512 MYSERIAL 5 MYDEVID 5
109 6 block 2147483648 512 MYSERIAL 6 MYDEVID 6
110 7 block 2147483648 512 MYSERIAL 7 MYDEVID 7
111 8 block 2147483648 512 MYSERIAL 8 MYDEVID 8
112 9 block 2147483648 512 MYSERIAL 9 MYDEVID 9
113 10 block 2147483648 512 MYSERIAL 10 MYDEVID 10
114 11 block 2147483648 512 MYSERIAL 11 MYDEVID 11
116 - You can see the LUN type and backing store for block/file backend LUNs
120 LUN Backend Size (Blocks) BS Serial Number Device ID
121 0 block 2147483648 512 MYSERIAL 0 MYDEVID 0
125 1 block 2147483648 512 MYSERIAL 1 MYDEVID 1
129 2 block 2147483648 512 MYSERIAL 2 MYDEVID 2
133 3 block 2147483648 512 MYSERIAL 3 MYDEVID 3
137 4 block 2147483648 512 MYSERIAL 4 MYDEVID 4
141 5 block 2147483648 512 MYSERIAL 5 MYDEVID 5
145 6 block 2147483648 512 MYSERIAL 6 MYDEVID 6
149 7 block 2147483648 512 MYSERIAL 7 MYDEVID 7
153 8 block 2147483648 512 MYSERIAL 8 MYDEVID 8
157 9 block 2147483648 512 MYSERIAL 9 MYDEVID 9
161 10 ramdisk 0 0 MYSERIAL 0 MYDEVID 0
163 11 ramdisk 204800000000000 512 MYSERIAL 1 MYDEVID 1
169 - Added in the second HA mode (where CTL does the data transfers instead
170 of having data transfers done below CTL), and abstracted out the Copan
173 - Fixed the phantom device problem in the CTL CAM SIM and improved the
174 CAM SIM to automatically trigger a rescan when the port is enabled and
177 - Made the number of threads in the block backend configurable via sysctl,
178 loader tunable and the ctladm command line. (You can now specify
179 -o num_threads=4 when creating a LUN with ctladm create.)
181 - Fixed some LUN selection issues in ctlstat(8) and allowed for selection
182 of LUN numbers up to 1023.
186 - This version intended for public release.
190 - Added descriptor sense support to CTL. It can be enabled through the
191 control mode page (10), but is disabled by default.
193 - Improved error injection support. The number of errors that can be
194 injected with 'ctladm inject' has been increased, and any arbitrary
195 sense data may now be injected as well.
197 - The port infrastructure has been revamped. Individual ports and types
198 of ports may now be enabled and disabled from the command line. ctladm
199 now has the ability to set the WWNN and WWPN for each port.
201 - The block backend can now send multiple I/Os to backing files. Multiple
202 writes are only allowed for ZFS, but multiple readers are allowed for
205 - The block and ramdisk backends now support setting the LUN blocksize.
206 There are some restrictions when the backing device is a block device,
207 but otherwise the blocksize may be set to anything.
212 - CTL initialization process has been revamped. Instead of using an
213 ad-hoc method, it is now sequenced through SYSINIT() calls.
215 - A block/file backend has been added. This allows using arbitrary files
216 or block devices as a backing store.
218 - The userland LUN configuration interface has been completely rewritten.
219 Configuration is now done out of band.
221 - The ctladm(8) command line interface has been revamped, and is now
222 similar to camcontrol(8).
227 - Use devstat(9) for CTL's statistics collection. CTL uses a home-grown
228 statistics collection system that is similar to devstat(9). ctlstat
229 should be retired in favor of iostat, etc., once aggregation modes are
230 available in iostat to match the behavior of ctlstat -t and dump modes
231 are available to match the behavior of ctlstat -d/ctlstat -J.
233 - ZFS ARC backend for CTL. Since ZFS copies all I/O into the ARC
234 (Adaptive Replacement Cache), running the block/file backend on top of a
235 ZFS-backed zdev or file will involve an extra set of copies. The
236 optimal solution for backing targets served by CTL with ZFS would be to
237 allocate buffers out of the ARC directly, and DMA to/from them directly.
238 That would eliminate an extra data buffer allocation and copy.
240 - Switch CTL over to using CAM CCBs instead of its own union ctl_io. This
241 will likely require a significant amount of work, but will eliminate
242 another data structure in the stack, more memory allocations, etc. This
243 will also require changes to the CAM CCB structure to support CTL.
248 CTL has the concept of pluggable frontend ports and backends. All
249 frontends and backends can be active at the same time. You can have a
250 ramdisk-backed LUN present along side a file backed LUN.
255 This is the core of CTL, where all of the command handlers and a lot of
256 other things live. Yes, it is large. It started off small and grew to its
257 current size over time. Perhaps it can be split into more files at some
260 Here is a roadmap of some of the primary functions in ctl.c. Starting here
261 and following the various leaf functions will show the command flow.
263 ctl_queue() This is where commands from the frontend ports come
266 ctl_queue_sense() This is only used for non-packetized SCSI. i.e.
267 parallel SCSI prior to U320 and perhaps U160.
269 ctl_work_thread() This is the primary work thread, and everything gets
272 ctl_scsiio_precheck() This where all of the initial checks are done, and I/O
273 is either queued for execution or blocked.
275 ctl_scsiio() This is where the command handler is actually
276 executed. (See ctl_cmd_table.c for the mapping of
277 SCSI opcode to command handler function.)
279 ctl_done() This is the routine called (or ctl_done_lock()) to
280 initiate the command completion process.
282 ctl_process_done() This is where command completion actually happens.
287 Basic function declarations and data structures.
293 These files define the basic CTL backend API. The comments in the header
299 The block and file backend. This allows for using a disk or a file as the
300 backing store for a LUN. Multiple threads are started to do I/O to the
301 backing device, primarily because the VFS API requires that to get any
304 ctl_backend_ramdisk.c:
305 ---------------------
307 A "fake" ramdisk backend. It only allocates a small amount of memory to
308 act as a source and sink for reads and writes from an initiator. Therefore
309 it cannot be used for any real data, but it can be used to test for
310 throughput. It can also be used to test initiators' support for extremely
316 This is a table with all 256 possible SCSI opcodes, and command handler
317 functions defined for supported opcodes. It is included in ctl.c.
322 Simplistic debugging support.
328 CTL-specific wrappers around the CAM sense building functions.
334 These files define the basic CTL frontend port API. The comments in the
335 header explain the API.
337 ctl_frontend_cam_sim.c:
338 ----------------------
340 This is a CTL frontend port that is also a CAM SIM. The idea is that this
341 frontend allows for using CTL without any target-capable hardware. So any
342 LUNs you create in CTL are visible via this port.
348 This is a High Availability API and TCP-based interlink implementation.
353 This defines most of the core CTL I/O structures. union ctl_io is
354 conceptually very similar to CAM's union ccb.
359 This defines all ioctls available through the CTL character device, and
360 the data structures needed for those ioctls.
365 Private data structres (e.g. CTL softc) and function prototypes. This also
366 includes the SCSI vendor and product names used by CTL.
372 CTL wrappers around CAM sense printing functions.
377 Command serialization table. This defines what happens when one type of
378 command is followed by another type of command. e.g., what do you do when
379 you have a mode select followed by a write? You block the write until the
380 mode select is complete. That is defined in this table.
386 CTL utility functions, primarily designed to be used from userland. See
387 ctladm for the primary consumer of these functions. These include CDB
393 CAM target peripheral driver and CTL frontend port. This is the path into
394 CTL for commands from target-capable hardware/SIMs.
399 ctladm(8) fills a role similar to camcontrol(8). It allow configuring LUNs,
400 issuing commands, injecting errors and various other control functions.
402 ctlstat(8) fills a role similar to iostat(8). It reports I/O statistics