Patent ID: 7467258

Claim:
A storage virtualizer, comprising: a plurality of targets being connectable to a host computer; means for connecting at least one physical storage unit to said targets via a plurality of paths; virtualization means producing at least one virtual storage unit by at least a part of a storage area of the physical storage unit and allowing the host computer to access to the virtual storage unit, said virtualization means real-accessing to the physical storage unit via the path corresponding to the target accessed when the access is executed; means for detecting failure of real access to the physical storage via each of the paths; target control means blocking the target corresponding to the failure path, which is detected by said detecting means, with respect to the host computer; and communication means for communicating with another multimode storage virtualizer, said communication means sending and receiving a datum, which indicates whether failure of real access, via paths connecting said another multimode storage virtualizer to the physical storage unit, occurs or not, wherein said target control means exceptionally blocks none of said targets or releases the block of all of said targets when said detecting means detects the failure in all of the paths connected to the physical storage unit and the datum, which indicates the failure occurring in all of the paths connecting said another multimode storage virtualizer to the physical storage unit, is received by said communication means.