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Documentation/cciss.txt 6.7 KB
1da177e4c   Linus Torvalds   Linux-2.6.12-rc2
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  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
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  	* SA P400i
  	* SA E200
  	* SA E200i
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  	* SA E500
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  Detecting drive failures:
  -------------------------
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  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
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  Device Naming:
  --------------
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  If nodes are not already created in the /dev/cciss directory, run as root:
  
  # cd /dev
  # ./MAKEDEV cciss
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  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 
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  (typically in /etc/init.d, but could vary depending on distribution). 
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  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.
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  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 
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  obey a reset command, though in most circumstances they will.  In
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  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.