Patent ID: 8862558

Claim:
A file storage system comprising: a controller for managing a plurality of files each having management information and actual data; a storage medium constituting a volume for storing the plurality of files, where the volume includes a first directory and a second directory, the first directory storing a first file and a second file; wherein the controller: creates a third file in a third directory and migrates the actual data of the second file to the third file; sets up the management information of the second file to refer to the third file so that the third file is reference when the second file receives a read access from the computer; compares a size of the actual data of the first file with a size of the actual data of the third file; if, as a result of the size comparison, the data sizes are identical, compares a binary of the actual data of the first file with a binary of the actual data of the third file; and if, as a result of the binary comparison, the binaries are identical, sets up the management information of the first file to refer to the third file so that the third file is referenced when the first file receives a read access from the computer, and deletes the first actual data, wherein the second directory is an index directory, wherein the third directory is provided in the second directory, the third file is created in the third directory in which the size of the third file is set as the directory name of the third directory, and wherein in order to compare the size of the actual data of the first file with size of the actual data of the third file, the controller compares the size of the actual data of the first file with the size denoted in the third directory name instead of the size of the actual data of the third file.