When performing migration of data from a migration source file server which is not endowed with any HSM interface, to a migration destination file server which is endowed with HSM, a volume of high capacity is needed for the migration destination file server, and moreover the performance deteriorates directly after the migration. However, with this system, the manager is enabled to set a migration policy using attribute information which can be acquired through a standard file access interface possessed by a file server program, and, when setting the attribute information of the migration destination file, the tier of the file which is to be created is determined, and the migration destination file is created, on the basis of this attribute information and migration policy.