Wednesday, 15 June 2011

Remove LUNS From Linux Safely



This post uses the QLogic Dynamic Target and LUN Discovery utilities. The steps below apply to SLES 10 and RHEL 5 servers using QLogic HBAs and PowerPath. This post also assumes that you have put the qlogic utilities into /tmp/ql_utils.



To remove a LUN and all associated PowerPath and Linux devices from the host environment follow these steps. 

Note: that it is critical to follow the procedures in exact order because deviating from the procedures can cause the host to panic

These steps were put together using steps from QLogic KB articles.

1. Stop any I/O to the device being removed. [Unmount the filesystem ] It is critical to stop all I/O on the device that is being removed.

2. Run the following command to determine which native SCSI devices are mapped to the pseudo device:

powermt display dev=all

Find the name of the LUN to be removed and match it up with the emcpower device name. This will need to be done on each server individually.

3. Run the command:

powermt remove dev=emcpower

Where corresponds to the LUN to be removed.

4. Run the command:

powermt release

Failing to run this command results in the pseudo device still being visible in /dev and /sys/block and may lead to some complications when the new devices are dynamically added.

5. In the /tmp/ql_utils directory, there should be a script to rescan the qlogic hbas. The script is called ql-dynamic-tgt-lun-disc.sh. Run the script:

/tmp/ql_utils/ql-dynamic-tgt-lun-disc.sh

6. You will now remove the device from the storage array using your array admin utilities. On the Linux server, run powermt display to verify that the device has been removed.

7. Now remove the LUN from the Storage Group (CLARiiON) or unmap it from the FA ports (DMX).

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