Hitachi Nondisruptive Migration moves data from HDS’ older Universal Storage Platform (USP) to the VSP. The target array spoofs the host operating system so it thinks it’s talking to the original system even as data is moved to the target. That allows applications to continue running during migration.

Patrick Allaire, an HDS senior product marketing manager, said this capability is based on three components:  a new persistent virtual Logical Device Identity (LDEV ID) that is used to manage multiple hosts, a logical identity takeover function, and Hitachi’s Universal Volume Manager (UVM).

The virtual LDEV ID is embedded in the SCSI layer of the Fibre Channel protocol. A virtual LDEV ID  is created and mapped from the source to the target, then the takeover function spoofs the operating system.  Finally, the Hitachi UVM copies or migrates the volume from the source to the VSP target.

Typically, a physical LDEV ID is used for this process but it makes it more manually intensive. “If you don’t have a virtual persistent ID, it forces you to do a shutdown of the application when changing the data path from the old storage system to the new one,” Allaire said.

With the new virtual LDEV ID and takeover function, Hitachi claims to maintain the quality of service levels for applications. Hitachi now supports host clustering configurations by synchronizing persistent group reserves on source volumes and keeping the host cluster operational. It also supports parallel migration of up to eight source systems to one Hitachi VSP.