Patent ID: 7565487

Claim:
A virtual storage subsystem, comprising: a plurality of storage subsystems each having a storage interface for storing data sent from a plurality of host computers, said data being stored in a storage extent; a plurality of virtual storage subsystems each providing a virtual storage extent associated with said storage extent and each having a first virtual storage interface and a second virtual storage interface; a management unit having stored therein performance information indicative of a utilization rate of each of the first virtual storage interfaces and logical network configuration information indicating in which logical networks each of the first virtual storage interfaces and each of the second virtual storage interfaces is included, a migration unit; and a migration command unit, wherein when performance of a first virtual storage subsystem that is in communication a first host computer and a first storage subsystem exceed a threshold value, said migration command unit selects a second virtual storage subsystem that can also communicate with said first host computer and said first storage subsystem, said second virtual storage subsystem having a first and second virtual storage interface determined in accordance with the logical network configuration information and, wherein said migration command unit issues a migration command to migrate a selected virtual storage extent provided by said first virtual storage system to said second virtual storage system, and said migration unit migrates the selected virtual storage extent provided by said first virtual storage subsystem to said second virtual storage subsystem.