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Diffstat (limited to 'Documentation/blockdev/cciss.txt')
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diff --git a/Documentation/blockdev/cciss.txt b/Documentation/blockdev/cciss.txt new file mode 100644 index 000000000..b79d0a13e --- /dev/null +++ b/Documentation/blockdev/cciss.txt @@ -0,0 +1,194 @@ +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 P700m + * SA P212 + * SA P410 + * SA P410i + * SA P411 + * SA P812 + * SA P712m + * SA P711m + +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 + +CCISS simple mode support +------------------------- + +The "cciss_simple_mode=1" boot parameter may be used to prevent the driver +from putting the controller into "performant" mode. The difference is that +with simple mode, each command completion requires an interrupt, while with +"performant mode" (the default, and ordinarily better performing) it is +possible to have multiple command completions indicated by a single +interrupt. + +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 engage the SCSI core at init +time if any tape drives or medium changers are detected. The driver may +also 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 best done via a script. + +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. This may be done via the /proc filesystem. +For example: + + echo "rescan" > /proc/scsi/cciss0/1 + +This causes the driver 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. It then notifies the SCSI mid layer +of these changes. + +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. + +There is a cciss_tape_cmds module parameter which can be used to make cciss +allocate more commands for use by tape drives. Ordinarily only a few commands +(6) are allocated for tape drives because tape drives are slow and +infrequently used and the primary purpose of Smart Array controllers is to +act as a RAID controller for disk drives, so the vast majority of commands +are allocated for disk devices. However, if you have more than a few tape +drives attached to a smart array, the default number of commands may not be +enought (for example, if you have 8 tape drives, you could only rewind 6 +at one time with the default number of commands.) The cciss_tape_cmds module +parameter allows more commands (up to 16 more) to be allocated for use by +tape drives. For example: + + insmod cciss.ko cciss_tape_cmds=16 + +Or, as a kernel boot parameter passed in via grub: cciss.cciss_tape_cmds=8 |