Migrating a virtual machine that uses 100% virtual disks is a simple task due to VMware Storage vMotion but migrating a VM that uses Raw Device Mappings from one array to another is somewhat trickier. There are options to convert a RDM into a virtual disk but that might not be feasible for applications that still require RDMs to be supported. Other options are host based mechanisms/in-guest mechanisms to copy the data from one device to another. That option sometimes can be complex and requires special drivers or even possibly downtime to fully finish the transition. To solve this issue for physical hosts, EMC introduced for the Symmetrix a feature called Federated Live Migration.
Federated Live Migration (FLM) allows the migration of a device from one Symmetrix array to another Symmetrix array without any downtime to the host and also does not affect the SCSI inquiry information of the original source device. Therefore, even though the device is now residing on a completely different Symmetrix array the host is none the wiser. FLM leverages Open Replicator functionality to migrate the data so it has some SAN requirements–the source array must be zoned to the target array. A FLM setup looks like the image below: