Patent ID: 8762679

Claim:
A storage system coupled to a host computer comprising: a plurality of storage devices which configures a plurality of logical units including a plurality of storage regions; and a controller configured to: provide a certain virtual volume including a plurality of virtual regions to the host computer; manage first storage regions of the plurality of storage regions and second storage regions of the plurality of storage regions, a size of the first storage region being different from size of the second storage region; determine which storage region is to be allocated to one of the plurality of virtual regions according to a size of data to be stored in the allocated storage region; allocate one of the first storage regions to a first virtual region of the certain virtual volume, the size of the first storage region being closer to a size of data to be stored in the first storage region than the size of the second storage region; and allocate one of the second storage regions to a second virtual region of the certain virtual volume, the size of the second storage region being closer to a size of data to be stored in the second storage region than size of first storage region.