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