One project I recently led is the migration of data from an old EMC Clariion to the new EMC VNX. There are a couple of strategies for migrating block data on a storage area network (SAN) – either use storage-based migration (migration is between the two storage arrays) or use host-based migration (migration is done on the host). EMC provides several tools for accomplishing these tasks. SAN Copy for instance is an excellent storage-based migration tool.

There are many factors to consider when choosing a migration strategy – size of data, cost, SAN bandwidth, complexity of the setup, application downtime, among many others. One strategy that is relatively simple and requires no downtime is to use the host-based migration tool PowerPath Migration Enabler Hostcopy.

This tool is part of PowerPath when you install the full software. In version 5.7 SP2, as long as the PowerPath is licensed, there is no additional license needed for Hostcopy (unlike the older version).

The migration process is non disruptive. It does not require shutting down the application. The host is still operational while migration is going on. In general, the steps for migrating data are:

1. On Windows or Linux host, make sure Powerpath 5.7 SP2 is installed and licensed.

powermt check_registration

2. Check source disk and record the disk pseudo name.

powermt display dev=all

3. On new storage, present the target LUN to host.

4. On host, rescan and initialize the target disk.

5. Check that the target disk is present and record the pseudo name.

powermt display dev=all

6. Setup the PowerPath Migration Enabler session

powermig setup -src harddiskXX -tgt harddiskYY -techType hostcopy

7. Perform initial synchronization

powermig sync -handle 1

8. Monitor status of the session

powermig query -handle 1

9. The data transfer rate can also be throttled

powermig throttle -throttleValue 0 -handle 1

10. When ready to switch over to the new storage, enter the following command:

powermig selectTarget -handle 1

11. Commit the changes

powermig commit -handle 1

12.Cleanup/delete the session

powermig cleanup -handle 1

13. Remove the old storage by removing lun from the old storage group

14. On host, rescan HBA for hardware changes, then remove old LUNs from PowerPath

powermt display dev=all
powermt remove dev=all
powermt display dev=all

For more information about PowerPath Migration Enabler, visit EMC website.