• Check the fstab for the devices that has to be removed.
• Be sure to unmount them!
• Check that you have uncommented or removed all ref. in /etc/fstab to the SAN LUN (Volume Group / Logical Volume)
• If LVM is used:

a. Remove the logical volumes

lvremove

b. Remove the volume groups

vgremove

c. Remove the physical volumes

pvremove

• Remove each path to the device from the SCSI subsystem. To do so, use the command echo 1 > /sys/block/device-name/device/delete where device-name may be sde, for example.

(Another variation of this operation is echo 1 > /sys/class/scsi_device/h:c:t:l/device/delete, where h is the HBA number, c is the channel on the HBA, t is the SCSI target ID, and l is the LUN)

a. Do this for every device name in the mpath that has to be removed:

b. Run multipath –ll to see the devices Eg. :

echo 1 > /sys/block/sdck/device/delete
echo 1 > /sys/block/sdcw/device/delete
echo 1 > /sys/block/sdi/device/delete
echo 1 > /sys/block/sdu/device/delete
echo 1 > /sys/block/sdce/device/delete
echo 1 > /sys/block/sdcq/device/delete
echo 1 > /sys/block/sdc/device/delete
echo 1 > /sys/block/sdo/device/delete

* If the device uses multipathing, run multipath -l and note all the paths to the device. 

NB! Note the wwn before you delete the multipath!

• Remove the multipathed device using multipath -f device.

multipath –f mpath0

• Ask SAN guys to remove the LUN(s).
• Reboot and follow startup from ILO

Thanks to Mikkel Arnberg for the input to this article.

Reference: http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/Online_Storage_Reconfiguration_Guide/removing_devices.html#clean-device-removal