Patent ID: 7058731

Claim:
A method for accessing physical storage from a host computer comprising: receiving I/O (input/output) requests from one or more applications in the host computer, the I/O requests being directed to a virtual storage volume; designating one of two or more storage systems as a target storage system; maintaining pairing information in the virtual storage volume, the pairing information relating to a pairing state of physical storage volumes which constitute the two or more storage systems; for each I/O request, producing one or more corresponding I/O operations that are directed to a target physical storage volume, the target physical storage volume being contained in the target system, the target physical storage volume being associated with the virtual storage volume; communicating the one or more corresponding I/O operations to the target storage system to service the I/O requests; and communicating a request to initiate a data copy process in which data in one of the storage systems, designated as the primary system, is copied to another of the storage systems, designated as the secondary system, wherein the primary system is designated as the target storage system.