Patent ID: 8447943

Claim:
A method of controlling a storage system, the method comprising: storing data in a first volume in the storage system which has volumes including the first volume and a plurality of second volumes; prohibiting write I/O (input/output) access against the first volume after storing the data in the first volume; performing subsequent write requests received by the storage system against the second volumes in the storage system after storing the data in the first volume, each write request having a target volume which is one of the second volumes; and in response to each one write request of the write requests, determining whether the target volume of the one write request is write prohibited or not, and performing the one write request only if the target volume is not write prohibited; wherein the second volumes are virtual volumes, which are allocated from a pool volume in units of pages in response to a write request, and wherein writing to the pages in the second volumes for performing the subsequent write requests are performed asynchronously.