A data element that is identical to a part of a plurality of data elements stored in a logical storage device (LU hereinbelow) is stored in a storage area (pool hereinbelow) separate from the LU. A first PDEV (physical storage device) that stores the data element stored in the LU may be placed in a power saving state while the storage system is operating (in periods when a read command can be received), and a second PDEV which stores the data element stored in the pool is not placed in a power saving state during operation. When the storage system receives a read command which is received from the host apparatus, and if the first PDEV is in the power saving state and a data element identical to the data element which is the target of the read command is stored in the pool, the storage system reads the identical data element from the pool without canceling the power saving state of the first PDEV, and sends the read data element to the host apparatus.