This invention enables a file to be accessed even during replication while maintaining its consistency. The replication is done among a plurality of distributed storage devices, a file is searched, in response to an access request from a client machine #11, from GUID management databases 13, 23 each of which stores a relationship between a GUID of a file stored in a storage device #0 (#1) and a device ID of a storage device containing an original file. When the storage device #1 does not have the demanded file, a device ID (#0) of a storage device containing its original file is searched from the GUID management database based on a GUID of the file C, and the file C demanded by this the storage device #0 is accessed.