Patent ID: 8868523

Claim:
A system comprising: a file server managing a plurality of files, the file server including a CPU and a memory; a local storage device coupled to the file server, the local storage device storing at least some of the files; a first file storage system coupled to the file server, which including a first file server and a first storage device, the first file storage system being able to be accessed by only specified users; and a second file storage system coupled to the file server, which including a second file server and a second storage device, the second file storage system being able to be accessed by unspecified users, wherein the memory stores: file management information including, for each of files, access control information defining a user which can access to the file, and storage management information including, for each of the local storage device, first file storage system and second file storage system, credibility information indicating whether high or low of its credibility determined by its difficulty for a leak of information and a falsification of information, wherein the credibility information of the first file storage system is higher than the credibility information of the second file storage system, wherein migration policy information associates one of the access control information with one of the credibility information, wherein the file server is configured to: specify one of the files whose access control information is updated, determine one of the local storage device, first file storage system and second file storage system in which the specified file is stored, when credibility information corresponds to the access control information of the specified file in the migration policy information is different from the credibility information managed for the determined storage system storing the specified file, migrate the specified file to a migration destination storage which is one of the local storage device, first file storage system and second file storage system having the credibility information managed as corresponding to the access control information of the specified file.