Patent ID: 7825799

Claim:
A storage system comprising: a plurality of storage devices for storing data to be used by a host computer; a controller for controlling to write data into at least one of the plurality of storage devices or to read data from at least one of the plurality of storage devices; a first power supply unit supplying power to the plurality of storage devices redundantly and comprising a first failure monitor circuit for monitoring a state of the first power supply unit and collecting a first failure information from the first power supply unit, and a first light emitting element for indicating failure occurred in the first power supply unit; and a second power supply unit supplying power to the plurality of storage devices and comprising a second failure monitor circuit for monitoring a state of the second power supply unit and collecting a second failure information from the second power supply unit, and a second light emitting element for indicating failure occurred in the second power supply unit, wherein, if the a first failure monitor circuit recognizes failure occurred in the first power supply unit by using the collected first failure information, the first failure monitor transfers the collected first failure information of the first power supply unit to the controller and the second failure monitor circuit, wherein the second failure monitor circuit receives the collected first failure information from the first failure monitor circuit, and transfers the received first failure information to the controller, and controls to light the first light emitting element in the first power supply unit, wherein the controller determines whether a failure is occurred or not based on the first failure information received from both the first and the second failure monitor circuits, and transfers a result of determination to the host computer, wherein the first power supply unit is adapted to be replaced based on the result of the determination.