LUN scan and resize operations with multipath on Ubuntu 12.04

Here are some quick tips to discover newly attached LUNs or to rescan resized LUNs:

Scan to discover a newly attached LUN:

1. for i in `ls /sys/class/fc_host`; do echo 1 > /sys/class/fc_host/${i}/issue_lip; done

Rescan resized LUN:

1. Find the path of your LUN:
   multipath -l
2. Execute following command to rescan your drives. Replace “dm-42” by the path you previously found:
   for i in `ls /sys/block/dm-42/slaves/`; do echo 1 > /sys/block/${i}/device/rescan ; done
3. Resize multipath device. Replace “dm-42” by the path you previously found:
   multipathd -k'resize map dm-42'
4. Resize the filesystem according to your needs.