Patent attributes
A storage apparatus which is connected via a network to a host which issues data I/O requests comprises storage devices of a plurality of types of varying performance, and a control unit which manages each storage area provided by each of the storage devices of a plurality of types by means of storage tiers of a plurality of different types, and which assigns storage areas in pre-determined units to virtual volumes from any storage tier among the storage tiers of a plurality of types in accordance with a data write request from the host, wherein, if there is an I/O request from the host, the control unit stores data corresponding to the I/O request in predetermined units in the cache memory and determines the storage tier of the storage area assigned to the virtual volume storing the data according to the mode of writing to the cache memory.
