Note that removing a SAN LUN (or disk) is a semi-tedious process that must be followed. Failure to do so will result in your server being left in a funky state. The process varries depending on how you are using your disk.
For Example: Is the disk part of a Logical Volume and under LVM control? Then shrink the volume group and then remove the disk from the volume group using pvremove.
vgreduce VolGroup <device name from `vgdisplay -v vgname` output>
pvremove <device name from `pvscan` output>
Kpartx & Multipath
Despite its name, its not a KDE-tool for partitioning disks.
Kpartx is a Partition device manager for device-mapper devices that is usually shipped as part of
multipath. Its purpose is to read the partition table of a device or a
file and create device map entries for the individual partitions.
When removing a disk from a system, you will need to remove the partition map of the multipathed device.
kpartx -d /dev/mapper/mpath5 <to remove the /dev/mapper/mpath5p1 device>
multipath -f mpath5 <where mpath5 is the alias for the multipathed device>
See example below:
mpath5 (360060e801004e780052fab2800000064) dm-7 HITACHI,DF600F
\_ round-robin 0 [prio=1][active]
\_ 3:0:0:3 sdj 8:144 [active][ready]
\_ 4:0:0:3 sdh 8:112 [active][ready]
Removing the disk from Linux Control.
This is the most important step, as not doing this part is what will screw up your box.
Then cd to the number of the SCSI device, for example 4:0:0:3 is the device id for /dev/sdh then type
echo 1 > device/delete