Patent ID: 7747799

Claim:
A storage system independent from a host computer comprising: a first logical volume to store data; and a control unit to migrate/compress data of the first logical volume having determination of whether a series of processes is necessary to be performed with a lookup of a LBA control table which indicates correspondence relationship between pre-migration/pre-compression and post-migration/post-compression, wherein the control unit includes a data conversion unit to compress and/or encrypt a first block set including N first blocks received from the host computer to a second block set including at least one second block to store the second block set in the first logical volume, N is an integer greater than or equal to 1, and when the control unit receives a write request for updating at least one of the N first blocks in the first block set, the control unit reads the second block set, decompresses the second block set to the first block set, generates an updated first block set by combining the at least one of the N first blocks with write data received according to the write request, compresses the updated first block set to an updated second block set, and stores the updated second block set in a storage area different from a storage area storing the second block set in the first logical volume.