Method and system for executing directory-basis migration in a global name space

Abstract

There has never been disclosed a method of executing migration on a fine-grained basis than a file system basis in a manner that is transparent to clients in a storage system with a plurality of servers to which a global name space is applied. In a storage system with a plurality of servers and a disk subsystem, which is coupled to the plurality of servers, a file system in the disk subsystem is assigned a first identifier, which is unique throughout the storage system, at least one of directories contained in the file system is assigned a second identifier, which is unique throughout the storage system, and a file contained in the file system is assigned a third identifier, which is unique throughout the file system. The server identifies a file below the directory that has the second identifier by the second identifier and by the third identifier.