At the time of a fan failure of a plurality of fans for cooling redundant controllers, data loss can be avoided even if a power source of each controller is controlled.A storage system includes: a first controller for controlling a first power source; a plurality of first fans for cooling the first controller; a second controller for controlling a second power source; a plurality of second fans for cooling the second controller; and a storage device including a plurality of storage units; wherein if a fan failure of the first fans occurs, the first controller controls the first power source in a standby state on condition that the second controller is in a normal state; and if the second power source is in the standby state, the first controller executes destaging processing and then controls the first power source in the standby state.