Patent ID: 7441009

Claim:
In a computer system comprising a host computer and a storage system including a plurality of physical storage units and a plurality of centralized modules respectively accessing to the assigned physical storage units, wherein the improvement comprises a storage virtualizer having: a plurality of connecting means for connecting to said host computer and the centralized modules; virtualization means producing at least one virtual storage unit by a part or the whole of storage areas of the physical storage units and allowing said host computer to access to the virtual storage unit, said virtualization means sending an access request to one of the centralized modules so as to access to the storage areas of the physical storage units corresponding to an access area of the virtual storage unit when said host computer accesses to the virtual storage unit; means for selecting the centralized module, which is assigned to deal with the storage areas of the physical storage units having the maximum storage capacity for the storage area of the corresponding virtual storage unit, for the virtual storage unit; and means for assigning the centralized module selected by said selecting means as the object centralized module, to which said virtualization means sends the access request, for the virtual storage unit.