STORAGE APPARATUS AND ITS CONTROL METHOD

摘要

A storage apparatus obtains a snapshot(s) of a first logical volume when needed and saves old data to a second logical volume when data is written to the first logical volume after obtaining the snapshot. A storage area of the second logical volume is allocated in chunk units to the first logical volume and a tendency of order to delete snapshots is judged when the chunks have been completely used up. If there is a tendency to delete the snapshots in their acquisition order, a new chunk is allocated to the first logical volume and a storage area in that chunk is determined to be a save location of the old data. If there is a tendency to delete the snapshots randomly, an unused storage area in a chunk already allocated to the first logical volume is determined to be the save location of the old data.