Aspects of the present invention relate to data migration and/or disaster recovery. One embodiment enables merging of bitmaps to allow for automation of the process of switching to a different target volume on the same storage subsystem without major interruption of data recovery capability and limited interruption of host I/O to the source volumes during the migration. In one approach, the migration of data onto a new target volume within the same storage subsystem as the original target volume is automated, without requiring the user to manually create or remove any new copy relationships.