Patent ID: 7664974

Claim:
A storage system, comprising: at least two loads, each load comprising at least one of: a channel adapter coupled to a host computer and receiving a read/write command sent from said host computer; a memory coupled to said channel adapter and storing data transferred from said channel adapter; a disk adapter coupled to said memory and transferring data stored in said memory to a plurality of storage regions; and a plurality of disk drive units having said storage regions and storing data transferred from said disk adapter; said storage system further comprising: at least two Direct Current (DC) power supply devices supplying DC power to said at least two loads, respectively; and at least three Alternate Current (AC) units having at least one breaker, said breaker interrupting supply of AC power if the AC power exceeds a certain level, and receiving AC power supplied from outside and supplying AC power to said at least two DC power supply devices, wherein a total of AC power supplied from said AC units is less than an amount of twice a DC power consumption of at least one load of said at least two loads.