FreeBSD/Linux Kernel Cross Reference
sys/Documentation/cciss.txt

     This driver is for Compaq's SMART Array Controllers.
     
     Supported Cards:
     ----------------
     
     This driver is known to work with the following cards:
     
             * SA 5300
             * SA 5i 
            * SA 532
            * SA 5312
            * SA 641
            * SA 642
            * SA 6400
            * SA 6400 U320 Expansion Module
            * SA 6i
            * SA P600
            * SA P800
            * SA E400
            * SA P400i
            * SA E200
            * SA E200i
            * SA E500
            * SA P212
            * SA P410
            * SA P410i
            * SA P411
            * SA P812
    
    Detecting drive failures:
    -------------------------
    
    To get the status of logical volumes and to detect physical drive
    failures, you can use the cciss_vol_status program found here:
    http://cciss.sourceforge.net/#cciss_utils
    
    Device Naming:
    --------------
    
    If nodes are not already created in the /dev/cciss directory, run as root:
    
    # cd /dev
    # ./MAKEDEV cciss
    
    You need some entries in /dev for the cciss device.  The MAKEDEV script
    can make device nodes for you automatically.  Currently the device setup
    is as follows:
    
    Major numbers:
            104     cciss0  
            105     cciss1  
            106     cciss2
            105     cciss3
            108     cciss4
            109     cciss5
            110     cciss6
            111     cciss7
    
    Minor numbers:
            b7 b6 b5 b4 b3 b2 b1 b0
            |----+----| |----+----|
                 |           |
                 |           +-------- Partition ID (0=wholedev, 1-15 partition)
                 |
                 +-------------------- Logical Volume number
    
    The device naming scheme is:
    /dev/cciss/c0d0                 Controller 0, disk 0, whole device
    /dev/cciss/c0d0p1               Controller 0, disk 0, partition 1
    /dev/cciss/c0d0p2               Controller 0, disk 0, partition 2
    /dev/cciss/c0d0p3               Controller 0, disk 0, partition 3
    
    /dev/cciss/c1d1                 Controller 1, disk 1, whole device
    /dev/cciss/c1d1p1               Controller 1, disk 1, partition 1
    /dev/cciss/c1d1p2               Controller 1, disk 1, partition 2
    /dev/cciss/c1d1p3               Controller 1, disk 1, partition 3
    
    SCSI tape drive and medium changer support
    ------------------------------------------
    
    SCSI sequential access devices and medium changer devices are supported and 
    appropriate device nodes are automatically created.  (e.g.  
    /dev/st0, /dev/st1, etc.  See the "st" man page for more details.) 
    You must enable "SCSI tape drive support for Smart Array 5xxx" and 
    "SCSI support" in your kernel configuration to be able to use SCSI
    tape drives with your Smart Array 5xxx controller.
    
    Additionally, note that the driver will not engage the SCSI core at init 
    time.  The driver must be directed to dynamically engage the SCSI core via 
    the /proc filesystem entry which the "block" side of the driver creates as 
    /proc/driver/cciss/cciss* at runtime.  This is because at driver init time, 
    the SCSI core may not yet be initialized (because the driver is a block 
    driver) and attempting to register it with the SCSI core in such a case 
    would cause a hang.  This is best done via an initialization script 
    (typically in /etc/init.d, but could vary depending on distribution). 
    For example:
    
            for x in /proc/driver/cciss/cciss[0-9]*
            do
                   echo "engage scsi" > $x
           done
   
   Once the SCSI core is engaged by the driver, it cannot be disengaged 
   (except by unloading the driver, if it happens to be linked as a module.)
   
   Note also that if no sequential access devices or medium changers are
   detected, the SCSI core will not be engaged by the action of the above
   script.
   
   Hot plug support for SCSI tape drives
   -------------------------------------
   
   Hot plugging of SCSI tape drives is supported, with some caveats.
   The cciss driver must be informed that changes to the SCSI bus
   have been made, in addition to and prior to informing the SCSI 
   mid layer.  This may be done via the /proc filesystem.  For example:
   
           echo "rescan" > /proc/scsi/cciss0/1
   
   This causes the adapter to query the adapter about changes to the 
   physical SCSI buses and/or fibre channel arbitrated loop and the 
   driver to make note of any new or removed sequential access devices
   or medium changers.  The driver will output messages indicating what 
   devices have been added or removed and the controller, bus, target and 
   lun used to address the device.  Once this is done, the SCSI mid layer 
   can be informed of changes to the virtual SCSI bus which the driver 
   presents to it in the usual way. For example: 
   
           echo scsi add-single-device 3 2 1 0 > /proc/scsi/scsi
    
   to add a device on controller 3, bus 2, target 1, lun 0.   Note that
   the driver makes an effort to preserve the devices positions
   in the virtual SCSI bus, so if you are only moving tape drives 
   around on the same adapter and not adding or removing tape drives 
   from the adapter, informing the SCSI mid layer may not be necessary.
   
   Note that the naming convention of the /proc filesystem entries 
   contains a number in addition to the driver name.  (E.g. "cciss0" 
   instead of just "cciss" which you might expect.)
   
   Note: ONLY sequential access devices and medium changers are presented 
   as SCSI devices to the SCSI mid layer by the cciss driver.  Specifically, 
   physical SCSI disk drives are NOT presented to the SCSI mid layer.  The 
   physical SCSI disk drives are controlled directly by the array controller 
   hardware and it is important to prevent the kernel from attempting to directly
   access these devices too, as if the array controller were merely a SCSI 
   controller in the same way that we are allowing it to access SCSI tape drives.
   
   SCSI error handling for tape drives and medium changers
   -------------------------------------------------------
   
   The linux SCSI mid layer provides an error handling protocol which
   kicks into gear whenever a SCSI command fails to complete within a
   certain amount of time (which can vary depending on the command).
   The cciss driver participates in this protocol to some extent.  The
   normal protocol is a four step process.  First the device is told
   to abort the command.  If that doesn't work, the device is reset.
   If that doesn't work, the SCSI bus is reset.  If that doesn't work
   the host bus adapter is reset.  Because the cciss driver is a block
   driver as well as a SCSI driver and only the tape drives and medium
   changers are presented to the SCSI mid layer, and unlike more 
   straightforward SCSI drivers, disk i/o continues through the block
   side during the SCSI error recovery process, the cciss driver only
   implements the first two of these actions, aborting the command, and
   resetting the device.  Additionally, most tape drives will not oblige 
   in aborting commands, and sometimes it appears they will not even 
   obey a reset command, though in most circumstances they will.  In
   the case that the command cannot be aborted and the device cannot be 
   reset, the device will be set offline.
   
   In the event the error handling code is triggered and a tape drive is
   successfully reset or the tardy command is successfully aborted, the 
   tape drive may still not allow i/o to continue until some command
   is issued which positions the tape to a known position.  Typically you
   must rewind the tape (by issuing "mt -f /dev/st0 rewind" for example)
   before i/o can proceed again to a tape drive which was reset.
   

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