1. A storage system, comprising: a secondary storage; a channel interface coupled to a server; a disk interface coupled to the secondary storage; a cache memory for temporarily storing data to be sent to and received from the secondary storage; and a processor; wherein a swap area of a main memory of the server is allocated to the secondary storage; and wherein the processor refers to data stored in the secondary storage and specifies the swap area, stores the specified swap area in the cache memory, and sends data of the swap area of the cache memory to the main memory of the server.