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Linus Torvalds1da177e2005-04-16 15:20:36 -07001This 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
Mike Miller9dc7a862005-09-13 01:25:19 -070020 * SA P400i
21 * SA E200
22 * SA E200i
Linus Torvalds1da177e2005-04-16 15:20:36 -070023
24If nodes are not already created in the /dev/cciss directory, run as root:
25
26# cd /dev
27# ./MAKEDEV cciss
28
29Device Naming:
30--------------
31
32You need some entries in /dev for the cciss device. The MAKEDEV script
33can make device nodes for you automatically. Currently the device setup
34is as follows:
35
36Major numbers:
37 104 cciss0
38 105 cciss1
39 106 cciss2
40 105 cciss3
41 108 cciss4
42 109 cciss5
43 110 cciss6
44 111 cciss7
45
46Minor numbers:
47 b7 b6 b5 b4 b3 b2 b1 b0
48 |----+----| |----+----|
49 | |
50 | +-------- Partition ID (0=wholedev, 1-15 partition)
51 |
52 +-------------------- Logical Volume number
53
54The device naming scheme is:
55/dev/cciss/c0d0 Controller 0, disk 0, whole device
56/dev/cciss/c0d0p1 Controller 0, disk 0, partition 1
57/dev/cciss/c0d0p2 Controller 0, disk 0, partition 2
58/dev/cciss/c0d0p3 Controller 0, disk 0, partition 3
59
60/dev/cciss/c1d1 Controller 1, disk 1, whole device
61/dev/cciss/c1d1p1 Controller 1, disk 1, partition 1
62/dev/cciss/c1d1p2 Controller 1, disk 1, partition 2
63/dev/cciss/c1d1p3 Controller 1, disk 1, partition 3
64
65SCSI tape drive and medium changer support
66------------------------------------------
67
68SCSI sequential access devices and medium changer devices are supported and
69appropriate device nodes are automatically created. (e.g.
70/dev/st0, /dev/st1, etc. See the "st" man page for more details.)
71You must enable "SCSI tape drive support for Smart Array 5xxx" and
72"SCSI support" in your kernel configuration to be able to use SCSI
73tape drives with your Smart Array 5xxx controller.
74
75Additionally, note that the driver will not engage the SCSI core at init
76time. The driver must be directed to dynamically engage the SCSI core via
77the /proc filesystem entry which the "block" side of the driver creates as
78/proc/driver/cciss/cciss* at runtime. This is because at driver init time,
79the SCSI core may not yet be initialized (because the driver is a block
80driver) and attempting to register it with the SCSI core in such a case
81would cause a hang. This is best done via an initialization script
82(typically in /etc/init.d, but could vary depending on distibution).
83For example:
84
85 for x in /proc/driver/cciss/cciss[0-9]*
86 do
87 echo "engage scsi" > $x
88 done
89
90Once the SCSI core is engaged by the driver, it cannot be disengaged
91(except by unloading the driver, if it happens to be linked as a module.)
92
93Note also that if no sequential access devices or medium changers are
94detected, the SCSI core will not be engaged by the action of the above
95script.
96
97Hot plug support for SCSI tape drives
98-------------------------------------
99
100Hot plugging of SCSI tape drives is supported, with some caveats.
101The cciss driver must be informed that changes to the SCSI bus
102have been made, in addition to and prior to informing the SCSI
103mid layer. This may be done via the /proc filesystem. For example:
104
105 echo "rescan" > /proc/scsi/cciss0/1
106
107This causes the adapter to query the adapter about changes to the
108physical SCSI buses and/or fibre channel arbitrated loop and the
109driver to make note of any new or removed sequential access devices
110or medium changers. The driver will output messages indicating what
111devices have been added or removed and the controller, bus, target and
112lun used to address the device. Once this is done, the SCSI mid layer
113can be informed of changes to the virtual SCSI bus which the driver
114presents to it in the usual way. For example:
115
116 echo scsi add-single-device 3 2 1 0 > /proc/scsi/scsi
117
118to add a device on controller 3, bus 2, target 1, lun 0. Note that
119the driver makes an effort to preserve the devices positions
120in the virtual SCSI bus, so if you are only moving tape drives
121around on the same adapter and not adding or removing tape drives
122from the adapter, informing the SCSI mid layer may not be necessary.
123
124Note that the naming convention of the /proc filesystem entries
125contains a number in addition to the driver name. (E.g. "cciss0"
126instead of just "cciss" which you might expect.)
127
128Note: ONLY sequential access devices and medium changers are presented
129as SCSI devices to the SCSI mid layer by the cciss driver. Specifically,
130physical SCSI disk drives are NOT presented to the SCSI mid layer. The
131physical SCSI disk drives are controlled directly by the array controller
132hardware and it is important to prevent the kernel from attempting to directly
133access these devices too, as if the array controller were merely a SCSI
134controller in the same way that we are allowing it to access SCSI tape drives.
135
mike.miller@hp.com3da8b712005-11-04 12:30:37 -0600136SCSI error handling for tape drives and medium changers
137-------------------------------------------------------
138
139The linux SCSI mid layer provides an error handling protocol which
140kicks into gear whenever a SCSI command fails to complete within a
141certain amount of time (which can vary depending on the command).
142The cciss driver participates in this protocol to some extent. The
143normal protocol is a four step process. First the device is told
144to abort the command. If that doesn't work, the device is reset.
145If that doesn't work, the SCSI bus is reset. If that doesn't work
146the host bus adapter is reset. Because the cciss driver is a block
147driver as well as a SCSI driver and only the tape drives and medium
148changers are presented to the SCSI mid layer, and unlike more
149straightforward SCSI drivers, disk i/o continues through the block
150side during the SCSI error recovery process, the cciss driver only
151implements the first two of these actions, aborting the command, and
152resetting the device. Additionally, most tape drives will not oblige
153in aborting commands, and sometimes it appears they will not even
154obey a reset coommand, though in most circumstances they will. In
155the case that the command cannot be aborted and the device cannot be
156reset, the device will be set offline.
157
158In the event the error handling code is triggered and a tape drive is
159successfully reset or the tardy command is successfully aborted, the
160tape drive may still not allow i/o to continue until some command
161is issued which positions the tape to a known position. Typically you
162must rewind the tape (by issuing "mt -f /dev/st0 rewind" for example)
163before i/o can proceed again to a tape drive which was reset.
164