There is provided a storage system accessed by a host computer, comprising: an interface coupled to the host computer; a processor coupled the interface; a memory coupled to the processor; and a storage device for storing the data. The storage device comprises a first storage device in which the stored data is accessed sequentially from a beginning, and a second storage device in which the stored data can be accessed at random. The data stored in the first storage device is replicated to the second storage device, and the replicated data is accessed by the host computer. The processor receives a candidate of the data including a priority of the data from the host computer, and replicates the data included in the candidate of the data, and stored in the first storage device to the second storage device in accordance with the priority before reception of an access request.