A storage system includes: a storage device including a recording medium that stores data and a device controller that executes addition processing involving a change of state of the data with respect to the data; and a storage controller that controls input and output of data for the storage device. The storage controller transmits, to the storage device, determination information that can be utilized by the device controller for determining whether or not to execute the addition processing along with input-output processing relating to input-output target data. The device controller controls execution of the addition processing with respect to the input-output target data based on the determination information transmitted from the storage controller.