Patent ID: 7257694

Claim:
A system for storing data comprising: a plurality of storage systems each of which comprises a controller and a disk; and a virtualization apparatus coupled to said plurality of storage systems; wherein said virtualization apparatus comprises: an input port to be coupled to a computer; an output port to be coupled to said plurality of storage systems; a control unit; and an access conversion table which is arranged to record matching relationships between virtual volumes which are targets of access requests from a computer and storage areas of said plurality of storage systems that are allocated to said virtual volumes; wherein said input port is arranged to receive a first write request issued by the computer to a virtual volume, said control unit makes an association between said virtual volume of said first write request and a real storage area in said plurality of storage systems if there is no matching relationship in said access conversion table between said virtual volume of said first write request and said storage areas of said plurality of storage systems, said control unit converts the first write request into a second write request for the real storage area, and said output port transfers said second write request converted based on said access conversion table to the real storage area associated with said virtual volume.