Patent ID: 8205054

Claim:
A storage system comprising: a plurality of storage devices that are the basis of pools of a plurality of types; and a controller that receives an I/O request that is a write request or a read request from a host computer and that performs an I/O processing that follows the I/O request, wherein the plurality of storage devices includes storage devices of a plurality of types having different performances, wherein the pools of a plurality of types are included in different layers, based on at least one storage device of the same type, pools of types corresponding to the type are configured, and wherein the pool of each type is configured by a plurality of real pages based on at least one storage device of the same type that is the basis of a pool, wherein the controller further comprises: an I/O processing section that allocates a real page that has not been allocated in a pool of any one type to a virtual page and that writes write targeted data that follows the received I/O request that is a write request to the allocated real page when the I/O processing section receives a write request in which a virtual page in a virtual volume that is a virtual logical volume composed of a plurality of virtual pages is specified from the host computer, if the real page has not been allocated to the specified virtual page as the I/O processing; and a storage location change processing section that performs storage location change processing in which a storage location of targeted data that has been stored to a targeted first real page allocated to a virtual page is changed to a second real page that has not been allocated in a pool of a second type different from a pool of a first type including the targeted first real page when the storage location change processing section conforms to prescribed storage location change conditions, wherein each virtual page is a virtual storage area, wherein each real page is a physical storage area, and wherein a size of a real page is different depending on a type of a pool.