Patent ID: 8880804

Claim:
A storage apparatus which is coupled to a host which issues a data I/O request via a network, comprising: storage devices of a plurality of types of varying performance; and a control unit configured to manage each of storage areas provided by the storage devices of the plurality of types by means of storage tiers of a plurality of different types, and to assign the storage areas in page units to a virtual volume from any of the storage tiers among the storage tiers of the plurality of types in response to a request to write the data from the host, wherein, if the data I/O request is received from the host, the control unit is configured to assign storage areas in page units from the uppermost storage tier to the target areas of the virtual volume corresponding to the data I/O request, and wherein the control unit is configured to change the page unit storage area assignment to predetermined areas of the virtual volume from an upper storage tier to a lower storage tier in accordance with the speed of processing of the data I/O request from the host, wherein the control unit is configured to take a blank area of a predetermined capacity of the uppermost storage tier according to a user designation, wherein the control unit is configured to calculate a time when unused capacity of the uppermost storage tier is depleted and time for securing the blank area on the basis of the speed of processing of the data I/O request from the host, and wherein, based on the time when the unused capacity is depleted and the time for securing the blank area, the control unit is configured to change page unit storage area assignment to predetermined areas of the virtual volume from the uppermost storage tier to a storage tier below the uppermost storage tier.