/Documentation/blockdev/cciss.txt

  1This driver is for Compaq's SMART Array Controllers.
  2
  3Supported Cards:
  4----------------
  5
  6This driver is known to work with the following cards:
  7
  8	* SA 5300
  9	* SA 5i 
 10	* SA 532
 11	* SA 5312
 12	* SA 641
 13	* SA 642
 14	* SA 6400
 15	* SA 6400 U320 Expansion Module
 16	* SA 6i
 17	* SA P600
 18	* SA P800
 19	* SA E400
 20	* SA P400i
 21	* SA E200
 22	* SA E200i
 23	* SA E500
 24	* SA P700m
 25	* SA P212
 26	* SA P410
 27	* SA P410i
 28	* SA P411
 29	* SA P812
 30	* SA P712m
 31	* SA P711m
 32
 33Detecting drive failures:
 34-------------------------
 35
 36To get the status of logical volumes and to detect physical drive
 37failures, you can use the cciss_vol_status program found here:
 38http://cciss.sourceforge.net/#cciss_utils
 39
 40Device Naming:
 41--------------
 42
 43If nodes are not already created in the /dev/cciss directory, run as root:
 44
 45# cd /dev
 46# ./MAKEDEV cciss
 47
 48You need some entries in /dev for the cciss device.  The MAKEDEV script
 49can make device nodes for you automatically.  Currently the device setup
 50is as follows:
 51
 52Major numbers:
 53	104	cciss0	
 54	105	cciss1	
 55	106	cciss2
 56	105	cciss3
 57	108	cciss4
 58	109	cciss5
 59	110	cciss6
 60	111	cciss7
 61
 62Minor numbers:
 63        b7 b6 b5 b4 b3 b2 b1 b0
 64        |----+----| |----+----|
 65             |           |
 66             |           +-------- Partition ID (0=wholedev, 1-15 partition)
 67             |
 68             +-------------------- Logical Volume number
 69
 70The device naming scheme is:
 71/dev/cciss/c0d0			Controller 0, disk 0, whole device
 72/dev/cciss/c0d0p1		Controller 0, disk 0, partition 1
 73/dev/cciss/c0d0p2		Controller 0, disk 0, partition 2
 74/dev/cciss/c0d0p3		Controller 0, disk 0, partition 3
 75
 76/dev/cciss/c1d1			Controller 1, disk 1, whole device
 77/dev/cciss/c1d1p1		Controller 1, disk 1, partition 1
 78/dev/cciss/c1d1p2		Controller 1, disk 1, partition 2
 79/dev/cciss/c1d1p3		Controller 1, disk 1, partition 3
 80
 81SCSI tape drive and medium changer support
 82------------------------------------------
 83
 84SCSI sequential access devices and medium changer devices are supported and 
 85appropriate device nodes are automatically created.  (e.g.  
 86/dev/st0, /dev/st1, etc.  See the "st" man page for more details.) 
 87You must enable "SCSI tape drive support for Smart Array 5xxx" and 
 88"SCSI support" in your kernel configuration to be able to use SCSI
 89tape drives with your Smart Array 5xxx controller.
 90
 91Additionally, note that the driver will not engage the SCSI core at init 
 92time.  The driver must be directed to dynamically engage the SCSI core via 
 93the /proc filesystem entry which the "block" side of the driver creates as 
 94/proc/driver/cciss/cciss* at runtime.  This is because at driver init time, 
 95the SCSI core may not yet be initialized (because the driver is a block 
 96driver) and attempting to register it with the SCSI core in such a case 
 97would cause a hang.  This is best done via an initialization script 
 98(typically in /etc/init.d, but could vary depending on distribution). 
 99For example:
100
101	for x in /proc/driver/cciss/cciss[0-9]*
102	do
103		echo "engage scsi" > $x
104	done
105
106Once the SCSI core is engaged by the driver, it cannot be disengaged 
107(except by unloading the driver, if it happens to be linked as a module.)
108
109Note also that if no sequential access devices or medium changers are
110detected, the SCSI core will not be engaged by the action of the above
111script.
112
113Hot plug support for SCSI tape drives
114-------------------------------------
115
116Hot plugging of SCSI tape drives is supported, with some caveats.
117The cciss driver must be informed that changes to the SCSI bus
118have been made.  This may be done via the /proc filesystem.
119For example:
120
121	echo "rescan" > /proc/scsi/cciss0/1
122
123This causes the driver to query the adapter about changes to the
124physical SCSI buses and/or fibre channel arbitrated loop and the
125driver to make note of any new or removed sequential access devices
126or medium changers.  The driver will output messages indicating what 
127devices have been added or removed and the controller, bus, target and 
128lun used to address the device.  It then notifies the SCSI mid layer
129of these changes.
130
131Note that the naming convention of the /proc filesystem entries 
132contains a number in addition to the driver name.  (E.g. "cciss0" 
133instead of just "cciss" which you might expect.)
134
135Note: ONLY sequential access devices and medium changers are presented 
136as SCSI devices to the SCSI mid layer by the cciss driver.  Specifically, 
137physical SCSI disk drives are NOT presented to the SCSI mid layer.  The 
138physical SCSI disk drives are controlled directly by the array controller 
139hardware and it is important to prevent the kernel from attempting to directly
140access these devices too, as if the array controller were merely a SCSI 
141controller in the same way that we are allowing it to access SCSI tape drives.
142
143SCSI error handling for tape drives and medium changers
144-------------------------------------------------------
145
146The linux SCSI mid layer provides an error handling protocol which
147kicks into gear whenever a SCSI command fails to complete within a
148certain amount of time (which can vary depending on the command).
149The cciss driver participates in this protocol to some extent.  The
150normal protocol is a four step process.  First the device is told
151to abort the command.  If that doesn't work, the device is reset.
152If that doesn't work, the SCSI bus is reset.  If that doesn't work
153the host bus adapter is reset.  Because the cciss driver is a block
154driver as well as a SCSI driver and only the tape drives and medium
155changers are presented to the SCSI mid layer, and unlike more 
156straightforward SCSI drivers, disk i/o continues through the block
157side during the SCSI error recovery process, the cciss driver only
158implements the first two of these actions, aborting the command, and
159resetting the device.  Additionally, most tape drives will not oblige 
160in aborting commands, and sometimes it appears they will not even 
161obey a reset command, though in most circumstances they will.  In
162the case that the command cannot be aborted and the device cannot be 
163reset, the device will be set offline.
164
165In the event the error handling code is triggered and a tape drive is
166successfully reset or the tardy command is successfully aborted, the 
167tape drive may still not allow i/o to continue until some command
168is issued which positions the tape to a known position.  Typically you
169must rewind the tape (by issuing "mt -f /dev/st0 rewind" for example)
170before i/o can proceed again to a tape drive which was reset.
171