Patent ID: 8918613

Claim:
A storage apparatus coupled to a host computer, the storage apparatus comprising: storage devices of a plurality of types of varying performance, each of the storage devices belonging to one tier of a plurality of tiers according to a type of the storage devices; and a controller, which is communicably connected to an external terminal, wherein the controller is configured to: manage the storage devices of a same type as storage tiers of the same type; provide a virtual volume to the host computer; allocate a storage area provided by the storage devices of the storage tiers to a page of the virtual volume; manage a usage ratio of tiers indicated by the external terminal and predetermined for the virtual volume; and determine locatable capacity of each storage tier for the virtual volume by using the usage ratio of tiers, wherein the storage area allocated to the page is determined based on an access frequency related to the page, the usage ratio of tiers, and a RAID level indicated by the external terminal and predetermined for the virtual volume.