The present invention provides a storage control technique that leaves no failure in a file system of a secondary volume even if the secondary volume is split from a primary volume with no restriction on server access to volumes in a storage controller. This invention provides a system including: a host system 100; a storage controller 101 for performing data processing between a storage device and the host system in response to requests from the host system; and a management server 130. The storage controller has a controller 104 that performs release processing to release mirroring between a primary volume 102 and a secondary volume 103 with access from the host system to the primary volume being permitted. The management server 130 executes a management program for examining volume management information about the secondary volume after the release processing.