Patent ID: 7451284

Claim:
A storage system provided with a storage control unit and a disk unit comprised of a plurality of physical storage devices, wherein the storage control unit comprises: a data transfer control unit controlling a data transfer with respect to a host machine and the disk unit; a cache memory temporarily storing the data; and a shared memory in which a configuration information of the storage system is stored, and wherein, in response to receiving an instruction to calculate a capacity necessary to acquire a snap shot which makes it possible to refer to the data within the disk unit at a certain time point, a monitoring interval being specified at the time the instruction is received, the storage control unit monitors a write instruction from the host machine for a predetermined period determined in accordance with the monitoring interval, and thereafter calculates the capacity necessary at the time of the snap shot, on the basis of the write requests monitored during the predetermined period, wherein the monitoring interval corresponds to a single snapshot generation and the predetermined period includes two or more snapshot generations, and wherein the storage control unit provides an operation plan of the snap shot including the calculation result of the capacity necessary at the time of acquiring the snap shot, said operation plan corresponding to the instruction to calculate and being displayed on the host machine or a service processor connected to the storage system and indicating whether a current storage capacity of the storage system is available to acquire the snap shot.