Patent ID: 7827269

Claim:
A file server coupled to a plurality of storage systems each including a plurality of Logical units (LUs) and a plurality of ports, comprising: a processor controlling a file access request from a client computer to one of the plurality of LUs stored in at least one of the plurality of storage systems; and a memory storing correspondence information between a plurality of target IDs associated to the WWN (World Wide Name) of each of the ports of the plurality of storage systems; wherein the processor acquires a maximum LU number, which is a value prepared beforehand and expressing a maximum number of LUs stored in the plurality of storage systems, in respect of a single port of the storage systems, wherein the processor acquires a first target ID from the plurality of target IDs in order to allocate the first target ID to a certain LUN (logical unit number) which is not allocated to any of the plurality of target IDs, wherein the processor determines that a first LUN is not allocated to any of the plurality of target IDs and assigns an unique device ID showing an order of the LUs of the plurality of storage systems, to the first LUN by calculating a formula that multiplies the first target ID and the maximum LU number and adds the first LUN, wherein the processor creates a device file having a device filename including the unique device ID corresponding to the first LUN, wherein a format of device information corresponding to the LU, managed by a UNIX-based OS, is divided to a major space including a type of the device and a minor space representing a space other than the major space in the format, and wherein the unique device ID is a specified number registered in the minor space.