A storage system, which includes a plurality of ODDs, is configured so as to easily retrieving a predetermined file from files stored in a plurality of optical discs. The storage system includes a storage controller connected to the plurality of ODDs and a nonvolatile memory via a storage bus. Each of the optical discs mounted in the ODDs has a file system representing the storage structure of files stored in the optical disc. The nonvolatile memory stores copies of the file systems of all the mounted optical discs. A user refers to the file system stored in the nonvolatile memory to retrieve a file. When an optical disc is ejected, the optical disc stores copies of the file systems of the other optical discs and is ejected. If the optical disc is installed into another storage system, the user can search for a file stored in the other optical discs.