Patent ID: 8200965

Claim:
A storage system, comprising: a host interface connected via a network to a host computer; a disk interface connected to a disk drive; a memory module that stores control information of the storage system and that functions as a cache memory; a processor that controls the storage system; a mutual network that interconnects the host interface, the disk interface, the memory module and the processor; and an encryption module that encrypts data read/written by the host computer, wherein a first logical volume and a second logical volume are set in the disk drive, and the first logical volume and the second logical volume are paired with each other, wherein the memory module stores a first encryption key assigned to the first logical volume and a second encryption key, which is different from the first encryption key, assigned to the second logical volume, wherein the encryption module encrypts data to be written in the first logical volume with the first encryption key, wherein the disk interface writes the data encrypted with the first encryption key in the first logical volume, wherein the encryption module encrypts data, which is a copy of the data written in the first logical volume, with the second encryption key, and wherein the disk interface writes the data encrypted with the second encryption key in the second logical volume.