An object of the present invention is to integrally manage disk storage apparatuses through virtualization. Some physical storage apparatuses 14 connected to a host computer 10 via a communication network 12 are virtualized with a virtual switch 18, a control unit 20, and a virtual device 22. The physical storage apparatus specifies a command when receiving the command from the host computer 10, and accesses, if the command access has been made to its own physical storage apparatus, a real disk via the virtual control unit 20 and virtual device 22, and executes I/O processing. If the command access is not made to its own physical storage apparatus, the physical storage apparatus 14 directs the command to the transmission target via the virtual switch 18. The physical storage apparatuses 14 are integrally managed according to the command in the above described manner.