Patent ID: 7296166

Claim:
A disk array system comprising: at least one disk controller including: at least one channel control unit for receiving an input/output request of data from an information processor and exchanging said data with said information processor, at least one disk control unit for exchanging said data with a disk drive in accordance with said input/output request, a cache memory unit for storing said data exchanged between said channel control unit and said disk control unit, a plurality of power units each for supplying power to one of said at least one disk control unit, and said cache memory unit, a casing for storing said at least one channel control unit, said at least one disk control unit, and said cache memory unit; and a plurality of Hard Disk Drive (HDD) boxes each including at least one disk drive controlled by said at least one disk control unit, wherein said at least one disk control unit performs a destaging process such that data stored in said cache memory unit that has not been written in the at least one disk drive is written in the at least one disk drive, wherein said disk array system controls to stop supplying power to a disk drive, said disk drive having finished the destaging process, on a disk drive by disk drive, and wherein said disk array system controls to compare voltage of power supplied to the power units to a predetermined value and if the voltage is less than the predetermined value outputs a notice to the at least one disk control unit.