A disk array control apparatus controls a disk array having a redundant configuration with two or more disk devices and a spare disk provided for lack of redundancy in the disk array. Since the light rays of two neighboring lamps overlap at the top surface of the shield, it is possible to provide a smooth change of the brightness between an area illuminated by two lamps and an area illuminated by only one lamp. In an embodiment according to the present invention, the update agent may also employ a flash library supporting multiple FLASH memory chips from the same or different manufacturers. The security system is constructed using the apparatus of generating the plane, beam or conical beam.