DEVICE NODES¶

The device naming scheme 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

FILES IN /proc¶

The files /proc/driver/cciss/cciss[0-9]+ contain information about the configuration of each controller. For example:

	someone@somehost:/proc/driver/cciss> ls -l
	total 0
	-rw-r--r-- 1 root root 0 2010-09-10 10:38 cciss0
	-rw-r--r-- 1 root root 0 2010-09-10 10:38 cciss1
	-rw-r--r-- 1 root root 0 2010-09-10 10:38 cciss2
	someone@somehost:/proc/driver/cciss> cat cciss2
	cciss2: HP Smart Array P800 Controller
	Board ID: 0x3223103c
	Firmware Version: 7.14
	IRQ: 16
	Logical drives: 1
	Current Q depth: 0
	Current # commands on controller: 0
	Max Q depth since init: 1
	Max # commands on controller since init: 2
	Max SG entries since init: 32
	Sequential access devices: 0
	cciss/c2d0:	  36.38GB	RAID 0
	someone@somehost:/proc/driver/cciss>

FILES IN /sys¶

/sys/bus/pci/devices/<dev>/ccissX/cXdY/model

Displays the SCSI INQUIRY page 0 model for logical drive Y of controller X.

/sys/bus/pci/devices/<dev>/ccissX/cXdY/rev

Displays the SCSI INQUIRY page 0 revision for logical drive Y of controller X.

/sys/bus/pci/devices/<dev>/ccissX/cXdY/unique_id

Displays the SCSI INQUIRY page 83 serial number for logical drive Y of controller X.

/sys/bus/pci/devices/<dev>/ccissX/cXdY/vendor

Displays the SCSI INQUIRY page 0 vendor for logical drive Y of controller X.

/sys/bus/pci/devices/<dev>/ccissX/cXdY/block:cciss!cXdY

A symbolic link to /sys/block/cciss!cXdY

/sys/bus/pci/devices/<dev>/ccissX/rescan

Kicks off a rescan of the controller to discover logical drive topology changes.

/sys/bus/pci/devices/<dev>/ccissX/cXdY/lunid

Displays the 8-byte LUN ID used to address logical drive Y of controller X.

/sys/bus/pci/devices/<dev>/ccissX/cXdY/raid_level

Displays the RAID level of logical drive Y of controller X.

/sys/bus/pci/devices/<dev>/ccissX/cXdY/usage_count

Displays the usage count (number of opens) of logical drive Y of controller X.

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.