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Documentation / blockdev / cciss.txt




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Based on kernel version 3.16. Page generated on 2014-08-06 21:36 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 P700m
25		* SA P212
26		* SA P410
27		* SA P410i
28		* SA P411
29		* SA P812
30		* SA P712m
31		* SA P711m
32	
33	Detecting drive failures:
34	-------------------------
35	
36	To get the status of logical volumes and to detect physical drive
37	failures, you can use the cciss_vol_status program found here:
38	http://cciss.sourceforge.net/#cciss_utils
39	
40	Device Naming:
41	--------------
42	
43	If nodes are not already created in the /dev/cciss directory, run as root:
44	
45	# cd /dev
46	# ./MAKEDEV cciss
47	
48	You need some entries in /dev for the cciss device.  The MAKEDEV script
49	can make device nodes for you automatically.  Currently the device setup
50	is as follows:
51	
52	Major 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	
62	Minor 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	
70	The 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	
81	CCISS simple mode support
82	-------------------------
83	
84	The "cciss_simple_mode=1" boot parameter may be used to prevent the driver
85	from putting the controller into "performant" mode. The difference is that
86	with simple mode, each command completion requires an interrupt, while with
87	"performant mode" (the default, and ordinarily better performing) it is
88	possible to have multiple command completions indicated by a single
89	interrupt.
90	
91	SCSI tape drive and medium changer support
92	------------------------------------------
93	
94	SCSI sequential access devices and medium changer devices are supported and 
95	appropriate device nodes are automatically created.  (e.g.  
96	/dev/st0, /dev/st1, etc.  See the "st" man page for more details.) 
97	You must enable "SCSI tape drive support for Smart Array 5xxx" and 
98	"SCSI support" in your kernel configuration to be able to use SCSI
99	tape drives with your Smart Array 5xxx controller.
100	
101	Additionally, note that the driver will engage the SCSI core at init
102	time if any tape drives or medium changers are detected.  The driver may
103	also be directed to dynamically engage the SCSI core via the /proc filesystem
104	entry which the "block" side of the driver creates as
105	/proc/driver/cciss/cciss* at runtime.  This is best done via a script.
106	
107	For example:
108	
109		for x in /proc/driver/cciss/cciss[0-9]*
110		do
111			echo "engage scsi" > $x
112		done
113	
114	Once the SCSI core is engaged by the driver, it cannot be disengaged 
115	(except by unloading the driver, if it happens to be linked as a module.)
116	
117	Note also that if no sequential access devices or medium changers are
118	detected, the SCSI core will not be engaged by the action of the above
119	script.
120	
121	Hot plug support for SCSI tape drives
122	-------------------------------------
123	
124	Hot plugging of SCSI tape drives is supported, with some caveats.
125	The cciss driver must be informed that changes to the SCSI bus
126	have been made.  This may be done via the /proc filesystem.
127	For example:
128	
129		echo "rescan" > /proc/scsi/cciss0/1
130	
131	This causes the driver to query the adapter about changes to the
132	physical SCSI buses and/or fibre channel arbitrated loop and the
133	driver to make note of any new or removed sequential access devices
134	or medium changers.  The driver will output messages indicating what 
135	devices have been added or removed and the controller, bus, target and 
136	lun used to address the device.  It then notifies the SCSI mid layer
137	of these changes.
138	
139	Note that the naming convention of the /proc filesystem entries 
140	contains a number in addition to the driver name.  (E.g. "cciss0" 
141	instead of just "cciss" which you might expect.)
142	
143	Note: ONLY sequential access devices and medium changers are presented 
144	as SCSI devices to the SCSI mid layer by the cciss driver.  Specifically, 
145	physical SCSI disk drives are NOT presented to the SCSI mid layer.  The 
146	physical SCSI disk drives are controlled directly by the array controller 
147	hardware and it is important to prevent the kernel from attempting to directly
148	access these devices too, as if the array controller were merely a SCSI 
149	controller in the same way that we are allowing it to access SCSI tape drives.
150	
151	SCSI error handling for tape drives and medium changers
152	-------------------------------------------------------
153	
154	The linux SCSI mid layer provides an error handling protocol which
155	kicks into gear whenever a SCSI command fails to complete within a
156	certain amount of time (which can vary depending on the command).
157	The cciss driver participates in this protocol to some extent.  The
158	normal protocol is a four step process.  First the device is told
159	to abort the command.  If that doesn't work, the device is reset.
160	If that doesn't work, the SCSI bus is reset.  If that doesn't work
161	the host bus adapter is reset.  Because the cciss driver is a block
162	driver as well as a SCSI driver and only the tape drives and medium
163	changers are presented to the SCSI mid layer, and unlike more 
164	straightforward SCSI drivers, disk i/o continues through the block
165	side during the SCSI error recovery process, the cciss driver only
166	implements the first two of these actions, aborting the command, and
167	resetting the device.  Additionally, most tape drives will not oblige 
168	in aborting commands, and sometimes it appears they will not even 
169	obey a reset command, though in most circumstances they will.  In
170	the case that the command cannot be aborted and the device cannot be 
171	reset, the device will be set offline.
172	
173	In the event the error handling code is triggered and a tape drive is
174	successfully reset or the tardy command is successfully aborted, the 
175	tape drive may still not allow i/o to continue until some command
176	is issued which positions the tape to a known position.  Typically you
177	must rewind the tape (by issuing "mt -f /dev/st0 rewind" for example)
178	before i/o can proceed again to a tape drive which was reset.
179	
180	There is a cciss_tape_cmds module parameter which can be used to make cciss
181	allocate more commands for use by tape drives.  Ordinarily only a few commands
182	(6) are allocated for tape drives because tape drives are slow and
183	infrequently used and the primary purpose of Smart Array controllers is to
184	act as a RAID controller for disk drives, so the vast majority of commands
185	are allocated for disk devices.  However, if you have more than a few tape
186	drives attached to a smart array, the default number of commands may not be
187	enought (for example, if you have 8 tape drives, you could only rewind 6
188	at one time with the default number of commands.)  The cciss_tape_cmds module
189	parameter allows more commands (up to 16 more) to be allocated for use by
190	tape drives.  For example:
191	
192	        insmod cciss.ko cciss_tape_cmds=16
193	
194	Or, as a kernel boot parameter passed in via grub:  cciss.cciss_tape_cmds=8
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