For a storage system which holds backup data of a first data storage extent in one or more second data storage extents in use of a first backup method, a backup status in a first backup method in a prescribed period is acquired and a first backup performance in a first backup configuration is computed based on this backup status. Meanwhile, a second backup performance in a second backup configuration is estimated based on a prescribed assumption in a prescribed period. Information is outputted based on the computed first backup performance and the estimated second backup performance.