Patent ID: 7313579

Claim:
A network storage system having a first network storage device for storing a file that is supplied to a client and a second network storage device that is connected to the client and the first network storage device, comprising: a file tree generation unit that generates a second file tree, which has the same structure as that of a first file tree of the first network storage device, on the second network storage device as a hierarchical directory structure of a file system thereof without transferring data in files of the first file tree to the second network storage device; a file specifying unit for specifying an access target file on the first network storage device that is requested by the client on the basis of an access request made to the second network storage device by the client in order to access the access target file on the first network storage device; and a file transfer unit that acquires attributes and data of the specified access target file from the first network storage device and stores the acquired attributes and data in a predetermined location in the second file tree, wherein the file specifying unit enables the client to follow the second file tree on the second network storage device from a root directory thereof downward to indicate the access target file thereon, after the second file tree is generated on the second network storage device; the file specifying unit acquires first file identifying information for specifying the access target file on the first network storage device from the first network storage device, when the client indicates the access target file in the second file tree by following the second file tree; the file specifying unit issues second file identifying information for specifying the access target file on the second network storage device, and communicates the issued second file identifying information to the client; the file specifying unit associates the first file identifying information acquired from the first network storage device with the issued second file identifying information, and manages the associated first and second file identifying information; when the second network storage device receives from the client an access request for accessing the access target file designating the second file identifying information, the file specifying unit converts the second file identifying information designed in the access request into the first identifying information associated therewith; the file transfer unit acquires data of the access target file from the first network storage device by using the converted first file identifying information and the file transfer unit stores the data of the access target file acquired from the first network storage device in the second file tree on the second network storage device, and provides the acquired data of the access target file for the client to access.