Documentation/cciss.txt

   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, in addition to and prior to informing the SCSI
 116 mid layer.  This may be done via the /proc filesystem.  For example:
 117
 118         echo "rescan" > /proc/scsi/cciss0/1
 119
 120 This causes the adapter 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.  Once this is done, the SCSI mid layer
 126 can be informed of changes to the virtual SCSI bus which the driver
 127 presents to it in the usual way. For example:
 128
 129         echo scsi add-single-device 3 2 1 0 > /proc/scsi/scsi
 130
 131 to add a device on controller 3, bus 2, target 1, lun 0.   Note that
 132 the driver makes an effort to preserve the devices positions
 133 in the virtual SCSI bus, so if you are only moving tape drives
 134 around on the same adapter and not adding or removing tape drives
 135 from the adapter, informing the SCSI mid layer may not be necessary.
 136
 137 Note that the naming convention of the /proc filesystem entries
 138 contains a number in addition to the driver name.  (E.g. "cciss0"
 139 instead of just "cciss" which you might expect.)
 140
 141 Note: ONLY sequential access devices and medium changers are presented
 142 as SCSI devices to the SCSI mid layer by the cciss driver.  Specifically,
 143 physical SCSI disk drives are NOT presented to the SCSI mid layer.  The
 144 physical SCSI disk drives are controlled directly by the array controller
 145 hardware and it is important to prevent the kernel from attempting to directly
 146 access these devices too, as if the array controller were merely a SCSI
 147 controller in the same way that we are allowing it to access SCSI tape drives.
 148
 149 SCSI error handling for tape drives and medium changers
 150 -------------------------------------------------------
 151
 152 The linux SCSI mid layer provides an error handling protocol which
 153 kicks into gear whenever a SCSI command fails to complete within a
 154 certain amount of time (which can vary depending on the command).
 155 The cciss driver participates in this protocol to some extent.  The
 156 normal protocol is a four step process.  First the device is told
 157 to abort the command.  If that doesn't work, the device is reset.
 158 If that doesn't work, the SCSI bus is reset.  If that doesn't work
 159 the host bus adapter is reset.  Because the cciss driver is a block
 160 driver as well as a SCSI driver and only the tape drives and medium
 161 changers are presented to the SCSI mid layer, and unlike more
 162 straightforward SCSI drivers, disk i/o continues through the block
 163 side during the SCSI error recovery process, the cciss driver only
 164 implements the first two of these actions, aborting the command, and
 165 resetting the device.  Additionally, most tape drives will not oblige
 166 in aborting commands, and sometimes it appears they will not even
 167 obey a reset command, though in most circumstances they will.  In
 168 the case that the command cannot be aborted and the device cannot be
 169 reset, the device will be set offline.
 170
 171 In the event the error handling code is triggered and a tape drive is
 172 successfully reset or the tardy command is successfully aborted, the
 173 tape drive may still not allow i/o to continue until some command
 174 is issued which positions the tape to a known position.  Typically you
 175 must rewind the tape (by issuing "mt -f /dev/st0 rewind" for example)
 176 before i/o can proceed again to a tape drive which was reset.
 177