Storage system, backup system, and backup method

摘要

A storage controller can perform backup processing without proceeding via a server and without the need for the server to grasp the state of pair volumes. When an instruction for backup is given from the server while data is being copied from a source volume to a target volume, the storage controller transfers the data to a backup device using differential information between the pair volumes after waiting until data about a range to be backed up and instructed by the server is copied into the target volume.