I recently had the opportunity to use the PowerPath Migration Enabler (PP/ME) to perform a seamless host-based LUN data migration from one SAN LUN to another on a fiber-attached host. PP/ME migrates the data and then swaps the LUN ID’s inside the guest OS, performing a seamless migration with no application downtime.

The PP/ME feature is an option when installing PowerPath. A free PP/ME license from EMC is required in addition to the PowerPath license. Once installed, the commands to perform the LUN migration are fairly straightforward. Start by presenting the new LUN to the host. The new LUN does not have to be on the same storage array as the old LUN.

In the command sequences below the target LUN = harddisk5 and the source LUN = harddisk6

Set up the migration with the command:

powermig setup -src harddisk6 -tgt harddisk5 -techType hostcopy

Begin copying data:

powermig sync -handle 1

Check the migration status:

powermig query -handle 1

When the data copy is complete the migration enters the “source selected” state and you can finalize the migration with these commands:

powermig selectTarget -handle 1
powermig commit -handle 1
powermig cleanup -handle 1
Once you’ve verified the host is using the new LUN the old LUN can be removed.