Patent ID: 7299333

Claim:
A storage system coupled to a plurality of computers, comprising: a plurality of inner logical volumes; and a controller controlling the plurality of inner logical volumes and having an LUN map, wherein the LUN map provides an association among a first outer LUN, a first computer ID, and a plurality of first inner LUNs, wherein the first outer LUN designates an outer logical volume, wherein the first computer ID identifies a computer which can access the outer logical volume by using the first outer LUN, wherein the outer logical volume comprises a first plurality of the inner logical volumes, wherein each of the first inner LUNs designates one of the first inner logical volumes, whereby one first inner logical volumes is accessed when the outer logical volume is accessed from the computer, wherein the controller is configured to receive a configuration change instruction that designates the plurality of first inner LUNs, wherein if there is a second inner logical volume having a storage capacity satisfying the received configuration change instruction, then the controller copies data stored on each of the first inner logical volumes to the second inner logical volume and modifies the LUN map so that the first outer LUN and the first computer ID are associated with a second inner LUN that designates the second inner logical volume, wherein subsequent to the configuration change instruction, the second inner logical volume is accessed when the outer logical volume is accessed from the computer.