Identifying LUN ID on Redhat Enterprise Linux

Applies to:

• RHEL v5 or newer
• Any other linux distro, I guess?

You can get the LUN ID info for certain LUN, by either performing several commands.

If you have multipath enabled, do:

[root@steelheart ~]# multipath -ll

The output should look like this:

mpath1 (200173800107503ed) dm-5 IBM,2450XIV
[size=480G][features=1 queue_if_no_path][hwhandler=0][rw]
\_ round-robin 0 [prio=12][active]
 \_ 5:0:3:2  sdaa 65:208 [active][ready]
 \_ 5:0:4:2  sdab 66:96  [active][ready]
 \_ 5:0:5:2  sdac 66:240 [active][ready]
 \_ 7:0:0:2  sdba 67:128 [active][ready]
 \_ 7:0:1:2  sdbb 68:16  [active][ready]
 \_ 7:0:2:2  sdbc 68:160 [active][ready]
 \_ 7:0:3:2  sdca 69:48  [active][ready]
 \_ 7:0:4:2  sdcb 69:192 [active][ready]
 \_ 7:0:5:2  sdcc 70:80  [active][ready]
 \_ 5:0:0:2  sdda  8:32   [active][ready]
 \_ 5:0:1:2  sddb  8:176  [active][ready]
 \_ 5:0:2:2  sddc  65:64  [active][ready]

The 4th digit is your LUN ID. In this case the LUN ID is “2”

If the server doesn’t use multipath, you can get the info by:

[root@steelheart ~]# ls -l /sys/block/*/device

This is the output, please scroll to the far right:

lrwxrwxrwx 1 root root 0 Jul 18 10:13 /sys/block/sdaa/device -> ../../devices/pci0000:00/0000:00:07.0/0000:1f:00.0/host5/rport-5:0-2/target5:0:2/5:0:2:14
lrwxrwxrwx 1 root root 0 Jul 18 10:13 /sys/block/sdab/device -> ../../devices/pci0000:00/0000:00:07.0/0000:1f:00.0/host5/rport-5:0-3/target5:0:3/5:0:3:14
lrwxrwxrwx 1 root root 0 Jul 18 10:13 /sys/block/sdac/device -> ../../devices/pci0000:00/0000:00:07.0/0000:1f:00.0/host5/rport-5:0-4/target5:0:4/5:0:4:14
lrwxrwxrwx 1 root root 0 Jul 18 10:13 /sys/block/sdba/device -> ../../devices/pci0000:00/0000:00:07.0/0000:1f:00.0/host5/rport-5:0-5/target5:0:5/5:0:5:14
lrwxrwxrwx 1 root root 0 Jul 18 10:13 /sys/block/sdbb/device -> ../../devices/pci0000:00/0000:00:09.0/0000:24:00.0/host7/rport-7:0-0/target7:0:0/7:0:0:14
lrwxrwxrwx 1 root root 0 Jul 18 10:13 /sys/block/sdbc/device -> ../../devices/pci0000:00/0000:00:09.0/0000:24:00.0/host7/rport-7:0-1/target7:0:1/7:0:1:14

In this case, the LUN ID for these disks are “14”

So, there you go 🙂