Patent ID: 7281107

Claim:
A storage system comprising: a storage device for providing a first logical device; a control memory for storing control information to prevent alteration of data written to the first logical device; and a controller for controlling data reading from and writing to the first logical device, based on the control information; wherein the control information includes: an alteration prevention deadline that indicates a deadline for prohibiting alteration of data written to the first logical device; a migration-permitted term that indicates a term for permitting data migration to a second logical device by the alteration prevention deadline for the data written in the first logical device; and data identification information for identifying whether the data written in the first logical device has been altered or not; and wherein conditional upon the data written to the first logical device, which has an alteration prevention setting, having been migrated without alteration to the second logical device during the migration-permitted term, the controller cancels the alteration prevention setting of the first logical device.