About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Documentation / cciss.txt

Based on kernel version 2.6.26. Page generated on 2008-07-16 21:12 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	
25	Detecting drive failures:
26	-------------------------
27	
28	To get the status of logical volumes and to detect physical drive
29	failures, you can use the cciss_vol_status program found here:
30	http://cciss.sourceforge.net/#cciss_utils
31	
32	Device Naming:
33	--------------
34	
35	If nodes are not already created in the /dev/cciss directory, run as root:
36	
37	# cd /dev
38	# ./MAKEDEV cciss
39	
40	You need some entries in /dev for the cciss device.  The MAKEDEV script
41	can make device nodes for you automatically.  Currently the device setup
42	is as follows:
43	
44	Major numbers:
45		104	cciss0	
46		105	cciss1	
47		106	cciss2
48		105	cciss3
49		108	cciss4
50		109	cciss5
51		110	cciss6
52		111	cciss7
53	
54	Minor numbers:
55	        b7 b6 b5 b4 b3 b2 b1 b0
56	        |----+----| |----+----|
57	             |           |
58	             |           +-------- Partition ID (0=wholedev, 1-15 partition)
59	             |
60	             +-------------------- Logical Volume number
61	
62	The device naming scheme is:
63	/dev/cciss/c0d0			Controller 0, disk 0, whole device
64	/dev/cciss/c0d0p1		Controller 0, disk 0, partition 1
65	/dev/cciss/c0d0p2		Controller 0, disk 0, partition 2
66	/dev/cciss/c0d0p3		Controller 0, disk 0, partition 3
67	
68	/dev/cciss/c1d1			Controller 1, disk 1, whole device
69	/dev/cciss/c1d1p1		Controller 1, disk 1, partition 1
70	/dev/cciss/c1d1p2		Controller 1, disk 1, partition 2
71	/dev/cciss/c1d1p3		Controller 1, disk 1, partition 3
72	
73	SCSI tape drive and medium changer support
74	------------------------------------------
75	
76	SCSI sequential access devices and medium changer devices are supported and 
77	appropriate device nodes are automatically created.  (e.g.  
78	/dev/st0, /dev/st1, etc.  See the "st" man page for more details.) 
79	You must enable "SCSI tape drive support for Smart Array 5xxx" and 
80	"SCSI support" in your kernel configuration to be able to use SCSI
81	tape drives with your Smart Array 5xxx controller.
82	
83	Additionally, note that the driver will not engage the SCSI core at init 
84	time.  The driver must be directed to dynamically engage the SCSI core via 
85	the /proc filesystem entry which the "block" side of the driver creates as 
86	/proc/driver/cciss/cciss* at runtime.  This is because at driver init time, 
87	the SCSI core may not yet be initialized (because the driver is a block 
88	driver) and attempting to register it with the SCSI core in such a case 
89	would cause a hang.  This is best done via an initialization script 
90	(typically in /etc/init.d, but could vary depending on distribution). 
91	For example:
92	
93		for x in /proc/driver/cciss/cciss[0-9]*
94		do
95			echo "engage scsi" > $x
96		done
97	
98	Once the SCSI core is engaged by the driver, it cannot be disengaged 
99	(except by unloading the driver, if it happens to be linked as a module.)
100	
101	Note also that if no sequential access devices or medium changers are
102	detected, the SCSI core will not be engaged by the action of the above
103	script.
104	
105	Hot plug support for SCSI tape drives
106	-------------------------------------
107	
108	Hot plugging of SCSI tape drives is supported, with some caveats.
109	The cciss driver must be informed that changes to the SCSI bus
110	have been made, in addition to and prior to informing the SCSI 
111	mid layer.  This may be done via the /proc filesystem.  For example:
112	
113		echo "rescan" > /proc/scsi/cciss0/1
114	
115	This causes the adapter to query the adapter about changes to the 
116	physical SCSI buses and/or fibre channel arbitrated loop and the 
117	driver to make note of any new or removed sequential access devices
118	or medium changers.  The driver will output messages indicating what 
119	devices have been added or removed and the controller, bus, target and 
120	lun used to address the device.  Once this is done, the SCSI mid layer 
121	can be informed of changes to the virtual SCSI bus which the driver 
122	presents to it in the usual way. For example: 
123	
124		echo scsi add-single-device 3 2 1 0 > /proc/scsi/scsi
125	 
126	to add a device on controller 3, bus 2, target 1, lun 0.   Note that
127	the driver makes an effort to preserve the devices positions
128	in the virtual SCSI bus, so if you are only moving tape drives 
129	around on the same adapter and not adding or removing tape drives 
130	from the adapter, informing the SCSI mid layer may not be necessary.
131	
132	Note that the naming convention of the /proc filesystem entries 
133	contains a number in addition to the driver name.  (E.g. "cciss0" 
134	instead of just "cciss" which you might expect.)
135	
136	Note: ONLY sequential access devices and medium changers are presented 
137	as SCSI devices to the SCSI mid layer by the cciss driver.  Specifically, 
138	physical SCSI disk drives are NOT presented to the SCSI mid layer.  The 
139	physical SCSI disk drives are controlled directly by the array controller 
140	hardware and it is important to prevent the kernel from attempting to directly
141	access these devices too, as if the array controller were merely a SCSI 
142	controller in the same way that we are allowing it to access SCSI tape drives.
143	
144	SCSI error handling for tape drives and medium changers
145	-------------------------------------------------------
146	
147	The linux SCSI mid layer provides an error handling protocol which
148	kicks into gear whenever a SCSI command fails to complete within a
149	certain amount of time (which can vary depending on the command).
150	The cciss driver participates in this protocol to some extent.  The
151	normal protocol is a four step process.  First the device is told
152	to abort the command.  If that doesn't work, the device is reset.
153	If that doesn't work, the SCSI bus is reset.  If that doesn't work
154	the host bus adapter is reset.  Because the cciss driver is a block
155	driver as well as a SCSI driver and only the tape drives and medium
156	changers are presented to the SCSI mid layer, and unlike more 
157	straightforward SCSI drivers, disk i/o continues through the block
158	side during the SCSI error recovery process, the cciss driver only
159	implements the first two of these actions, aborting the command, and
160	resetting the device.  Additionally, most tape drives will not oblige 
161	in aborting commands, and sometimes it appears they will not even 
162	obey a reset command, though in most circumstances they will.  In
163	the case that the command cannot be aborted and the device cannot be 
164	reset, the device will be set offline.
165	
166	In the event the error handling code is triggered and a tape drive is
167	successfully reset or the tardy command is successfully aborted, the 
168	tape drive may still not allow i/o to continue until some command
169	is issued which positions the tape to a known position.  Typically you
170	must rewind the tape (by issuing "mt -f /dev/st0 rewind" for example)
171	before i/o can proceed again to a tape drive which was reset.
Hide Line Numbers
About Kernel Documentation Linux Kernel Contact Linux Resources Linux Blog

Information is copyright its respective author. All material is available from the Linux Kernel Source distributed under a GPL License. This page is provided as a free service by mjmwired.net.