Patent ID: 8312246

Claim:
A storage system comprising: a plurality of storage devices: and a controller configured to: provide a plurality of virtual volumes to a host computer; manage: a plurality of logical units on the plurality of storage device; and a plurality of storage pools each including at least one of the plurality of logical units; allocate, in response to receiving a write request to a particular virtual volume belonging to the plurality of virtual volumes, a storage region of the plurality storage pools; and store data related to the write request in the storage region allocated to the particular virtual volume, wherein the controller is further configured to: allocate a first storage region in a first storage pool of the plurality of storage pools to a first virtual volume of the plurality of virtual volumes based on a first size of the first storage region or the first virtual volume, allocate a second storage region in a second storage pool of the plurality of storage pools to a second virtual volume of the plurality of virtual volumes based on a second size of the second storage region or the second virtual volume, wherein the second size is different from the first size.