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:
$ cd /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
$ 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
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-
When this file is written to, the driver rescans the controller to
discover any new, removed, or modified logical drives.
/sys/bus/pci/devices/dev/ccissX/resettable-
A value of 1 displayed in this file indicates that the
"reset_devices=1" kernel parameter (used by kdump) is
honored by this controller. A value of 0 indicates that the
"reset_devices=1" kernel parameter will not be honored. Some models of
Smart Array are not able to honor this parameter.
/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.
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 st(4)
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 run time.
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. 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
fiber channel arbitrated loop, and
make note of any new or removed sequential access devices or
medium changers.
The driver will output messages indicating which devices have been
added or removed and the controller, bus, target, and lun used to
address each device. The driver then notifies the SCSI midlayer 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 midlayer by the
cciss driver. Specifically, physical SCSI disk drives
are not presented to the SCSI midlayer. The only disk devices
that are presented to the kernel are logical drives that the array
controller constructs from regions on the physical drives. The logical
drives are presented to the block layer (not to the SCSI midlayer). It
is important for the driver to prevent the kernel from accessing the
physical drives directly, since these drives are used by the array
controller to construct the logical drives.
SCSI error handling for tape drives and medium changers
The Linux SCSI midlayer provides an error-handling protocol that is
initiated 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.
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 midlayer. Furthermore, unlike more straightforward SCSI drivers,
disk I/O continues through the block side during the SCSI error-recovery
process. Therefore, the cciss driver implements only
the first two of these actions, aborting the command, and resetting the
device. Note also that 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. If the command cannot
be aborted and the device cannot be reset, the device will be set
offline.
In the event that 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 that 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 that was
reset.