Migrating data with an equivalent amount of free capacity

To prevent managed disks (MDisks) from having an uneven distribution of data, ensure that the cluster has the same amount of free space as the data that you want to migrate.

1. Stop all I/O operations from the hosts. Unmap the logical disks that contain the data from the hosts.
2. Create one or more MDisk groups with free capacity. Ensure that the MDisk groups have enough free capacity to contain all of the migrating data and that they have balanced data distribution.
3. Create an empty MDisk group. This temporarily contains the data that is imported.
4. Perform the following steps to create an image mode virtual disk (VDisk) from the first unmanaged-mode MDisk that contains the data to be imported:
   1. Map one logical disk from the storage system to the SAN Volume Controller ports.
   2. Issue the svctask detectmdisk command-line interface (CLI) command on the cluster or use the SAN Volume Controller Console to discover MDisks. The new unmanaged-mode MDisk that is found corresponds with the logical disk mapped in the previous step.
   3. Create an image mode VDisk from this unmanaged-mode MDisk and assign it to the empty MDisk group that you just created.
   4. Repeat steps 4.a through 4.c for all logical disks as required.
5. You can restart host applications by mapping the image mode VDisks to the hosts and restarting the hosts. Alternatively, you can wait until the migration is complete to map the VDisks to the hosts.
6. Perform the following steps to migrate the data to the MDisk groups that you created in step 2:
   1. Select the first image mode VDisk to be migrated.
   2. Using the svctask migratevdisk or svctask migratetoimage command, migrate this VDisk from its current MDisk group to one of the MDisk groups that you created in step 2. This migrates all of the data from the logical disk into the new free space.
   3. Run the svcinfo lsmigrate command to verify that the migration has completed.
   4. Select the next image mode VDisk and repeat the previous step after the migration completes.
7. When all the VDisks have been migrated, the MDisk groups that you created in step 2 contain the data that was on the image mode VDisks. The data is striped across the new groups and is virtualized.
8. Destroy the temporary MDisk group that contained the original image mode VDisks.
9. Go back to the storage system and reconfigure the old arrays and logical disks according to the guidelines.
10. Add this storage back under the SAN Volume Controller and use the old storage to create new VDisks.