Patent ID: 8041682

Claim:
A storage system, comprising: a plurality of storage devices including a first type storage device and a second type storage device, a reliability attribute and/or a performance attribute of the first type storage device being different from a reliability attribute and/or a performance attribute of the second type storage device; and a control unit managing a plurality of virtual volumes, a plurality of first type storage areas and a plurality of second type storage areas, each of the plurality of virtual volumes being adapted to be accessed from an external device by specifying a logical unit number, the plurality of first type storage areas being provided with the first type storage device, the plurality of second type storage areas being provided with the second type storage device, wherein, if necessary, a storage area allocated to a first portion of a virtual volume of the plurality of virtual volumes is changed from a first type storage area of the plurality of first type storage areas to a second type storage area of the plurality of second type storage areas while another first type storage area of the plurality of first type storage areas is allocated to a second portion of the virtual volume.