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
168 - Added in the second HA mode (where CTL does the data transfers instead
169 of having data transfers done below CTL), and abstracted out the Copan
172 - Fixed the phantom device problem in the CTL CAM SIM and improved the
173 CAM SIM to automatically trigger a rescan when the port is enabled and
176 - Made the number of threads in the block backend configurable via sysctl,
177 loader tunable and the ctladm command line. (You can now specify
178 -o num_threads=4 when creating a LUN with ctladm create.)
180 - Fixed some LUN selection issues in ctlstat(8) and allowed for selection
181 of LUN numbers up to 1023.
185 - This version intended for public release.
189 - Added descriptor sense support to CTL. It can be enabled through the
190 control mode page (10), but is disabled by default.
192 - Improved error injection support. The number of errors that can be
193 injected with 'ctladm inject' has been increased, and any arbitrary
194 sense data may now be injected as well.
196 - The port infrastructure has been revamped. Individual ports and types
197 of ports may now be enabled and disabled from the command line. ctladm
198 now has the ability to set the WWNN and WWPN for each port.
200 - The block backend can now send multiple I/Os to backing files. Multiple
201 writes are only allowed for ZFS, but multiple readers are allowed for
204 - The block and ramdisk backends now support setting the LUN blocksize.
205 There are some restrictions when the backing device is a block device,
206 but otherwise the blocksize may be set to anything.
211 - CTL initialization process has been revamped. Instead of using an
212 ad-hoc method, it is now sequenced through SYSINIT() calls.
214 - A block/file backend has been added. This allows using arbitrary files
215 or block devices as a backing store.
217 - The userland LUN configuration interface has been completely rewritten.
218 Configuration is now done out of band.
220 - The ctladm(8) command line interface has been revamped, and is now
221 similar to camcontrol(8).
226 - Use devstat(9) for CTL's statistics collection. CTL uses a home-grown
227 statistics collection system that is similar to devstat(9). ctlstat
228 should be retired in favor of iostat, etc., once aggregation modes are
229 available in iostat to match the behavior of ctlstat -t and dump modes
230 are available to match the behavior of ctlstat -d/ctlstat -J.
232 - ZFS ARC backend for CTL. Since ZFS copies all I/O into the ARC
233 (Adaptive Replacement Cache), running the block/file backend on top of a
234 ZFS-backed zdev or file will involve an extra set of copies. The
235 optimal solution for backing targets served by CTL with ZFS would be to
236 allocate buffers out of the ARC directly, and DMA to/from them directly.
237 That would eliminate an extra data buffer allocation and copy.
239 - Switch CTL over to using CAM CCBs instead of its own union ctl_io. This
240 will likely require a significant amount of work, but will eliminate
241 another data structure in the stack, more memory allocations, etc. This
242 will also require changes to the CAM CCB structure to support CTL.
247 CTL has the concept of pluggable frontend ports and backends. All
248 frontends and backends can be active at the same time. You can have a
249 ramdisk-backed LUN present along side a file backed LUN.
254 This is the core of CTL, where all of the command handlers and a lot of
255 other things live. Yes, it is large. It started off small and grew to its
256 current size over time. Perhaps it can be split into more files at some
259 Here is a roadmap of some of the primary functions in ctl.c. Starting here
260 and following the various leaf functions will show the command flow.
262 ctl_queue() This is where commands from the frontend ports come
265 ctl_queue_sense() This is only used for non-packetized SCSI. i.e.
266 parallel SCSI prior to U320 and perhaps U160.
268 ctl_work_thread() This is the primary work thread, and everything gets
271 ctl_scsiio_precheck() This where all of the initial checks are done, and I/O
272 is either queued for execution or blocked.
274 ctl_scsiio() This is where the command handler is actually
275 executed. (See ctl_cmd_table.c for the mapping of
276 SCSI opcode to command handler function.)
278 ctl_done() This is the routine called (or ctl_done_lock()) to
279 initiate the command completion process.
281 ctl_process_done() This is where command completion actually happens.
286 Basic function declarations and data structures.
292 These files define the basic CTL backend API. The comments in the header
298 The block and file backend. This allows for using a disk or a file as the
299 backing store for a LUN. Multiple threads are started to do I/O to the
300 backing device, primarily because the VFS API requires that to get any
303 ctl_backend_ramdisk.c:
304 ---------------------
306 A "fake" ramdisk backend. It only allocates a small amount of memory to
307 act as a source and sink for reads and writes from an initiator. Therefore
308 it cannot be used for any real data, but it can be used to test for
309 throughput. It can also be used to test initiators' support for extremely
315 This is a table with all 256 possible SCSI opcodes, and command handler
316 functions defined for supported opcodes. It is included in ctl.c.
321 Simplistic debugging support.
327 CTL-specific wrappers around the CAM sense building functions.
333 These files define the basic CTL frontend port API. The comments in the
334 header explain the API.
336 ctl_frontend_cam_sim.c:
337 ----------------------
339 This is a CTL frontend port that is also a CAM SIM. The idea is that this
340 frontend allows for using CTL without any target-capable hardware. So any
341 LUNs you create in CTL are visible via this port.
347 This is a High Availability API and TCP-based interlink implementation.
352 This defines most of the core CTL I/O structures. union ctl_io is
353 conceptually very similar to CAM's union ccb.
358 This defines all ioctls available through the CTL character device, and
359 the data structures needed for those ioctls.
364 Private data structres (e.g. CTL softc) and function prototypes. This also
365 includes the SCSI vendor and product names used by CTL.
371 CTL wrappers around CAM sense printing functions.
376 Command serialization table. This defines what happens when one type of
377 command is followed by another type of command. e.g., what do you do when
378 you have a mode select followed by a write? You block the write until the
379 mode select is complete. That is defined in this table.
385 CTL utility functions, primarily designed to be used from userland. See
386 ctladm for the primary consumer of these functions. These include CDB
392 CAM target peripheral driver and CTL frontend port. This is the path into
393 CTL for commands from target-capable hardware/SIMs.
398 ctladm(8) fills a role similar to camcontrol(8). It allow configuring LUNs,
399 issuing commands, injecting errors and various other control functions.
401 ctlstat(8) fills a role similar to iostat(8). It reports I/O statistics