A plurality of contents intrinsic values that are values intrinsic to respective contents of a plurality of files stored in one or more first storage devices are calculated. Whether two or more identical contents intrinsic values are contained among the plurality of contents intrinsic values is determined. When two or more identical contents intrinsic values are present, an access destination of a first file corresponding to a first contents intrinsic value from among these two or more contents intrinsic values is changed to a position having stored therein a second file corresponding to a second contents intrinsic value from among these two or more contents intrinsic values.