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Documentation / cciss.txt




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Based on kernel version 2.6.27. Page generated on 2008-10-13 09:53 EST.

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