Patent 7461226 was granted and assigned to Hitachi on December, 2008 by the United States Patent and Trademark Office.
Two storage areas are created in a first storage subsystem, a synchronous remote copy is performed from a first storage area included in the first storage subsystem to a storage area included in a second storage subsystem, and an asynchronous remote copy is performed from a second storage area included in the first storage subsystem to a storage area included in a third storage subsystem. Besides, a computer accessing the first storage subsystem performs mirroring to both the storage areas included in the first storage subsystem.