Patent ID: 8650360

Claim:
A storage system coupled to a host apparatus, the storage system comprising: a controller; and a plurality of storage devices including a first type of storage devices and a second type of storage devices, an attribute of the first type of storage devices being different from an attribute of the second type of storage devices, the controller configured to: manage at least a pool including a plurality of real pages, each of which is included in one of the plurality of storage devices; provide a virtual volume to the host apparatus, the virtual volume including a plurality of virtual pages, to each of which a portion of the pool is allocated in accordance with a write command; distribute data written in a first virtual page to a first group of real pages, the first group of real pages being included in a portion of the pool allocated to the first virtual page, the first group of real pages making up a redundant array and being selected from different storage devices of the first type of storage devices; and migrate data stored in the first group of real pages to the second type of storage devices so that each real page of the first group belongs to the second type of storage devices according to an access status of the first virtual page.