Re: How to find which disk a LUN is mapped to

On Thu, 2009-04-30 at 13:25 +1200, Paul Ward wrote:
Hi all,

I need to find out which disk LUN6 points to on my RH3 box.

I have looked at /proc/scsi/scsi
This gives me LUNS from 00 to 05
Does this mean 05 is infact LUN06?

These days it's easiest to find this information from sysfs.

Under /sys/bus/scsi/devices you'll find sub-directories that list all
SCSI devices by their bus address (in host:bus:target:lun format). E.g.
if I want to find out what device 3:0:0:1 on my system is I can look at:

# ls /sys/bus/scsi/devices/3\:0\:0\:1/
block:sdd delete dh_state generic iodone_cnt
iorequest_cnt power queue_type rev
scsi_disk:3:0:0:1 scsi_level subsystem type vendor
bus device_blocked driver iocounterbits ioerr_cnt model
queue_depth rescan scsi_device:3:0:0:1 scsi_generic:sg3 state
timeout uevent

The first entry is a symlink that points back to the corresponding block
device, in this case /dev/sdd:

# ls -l /sys/bus/scsi/devices/3\:0\:0\:1/block\:sdd
lrwxrwxrwx 1 root root 0 Apr 30
10:06 /sys/bus/scsi/devices/3:0:0:1/block:sdd
-> ../../../../../../../../../block/sdd

All the symlinks can make navigating sysfs a bit daunting at first but
there's a wealth of useful information and knobs to tweak in there.
Tools like systool and udevinfo can also help to make it a bit easier to
digest.

Regards,
Bryn.


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