Patent ID: 8161239

Claim:
A computer system comprises: a first storage system and a second storage system each coupled to a host computer, each having first correspondence information regarding correspondence relationships between commands from the host computer and functions of the first and the second storage systems and second correspondence information regarding correspondence relationships between the functions and the storage systems that have the functions, a third storage system coupled to the first storage system and the second storage system, wherein one of the first and the second storage system is configured to provide a logical volume stored in the third storage system as a virtual volume to the host computer, wherein the host computer is configured to recognize the first and the second storage systems logically as a single virtual storage system, and wherein the host computer is configured to: generate a command to the virtual storage system; determine one of the first and second storage systems in possession of the function corresponding to the command by referring to the first and second correspondence information; and transfer the command to the one of the first and the second storage systems in possession of the function corresponding to the command by referring to the second correspondence information.