Provided is a storage system having a storage device including memory drives formed of the non-volatile memory, a group is constituted by the memory drives whose number is larger than the number of memory drives necessary to provide the memory capacity, the divided storage areas are managed in each of segments that includes at least one of the divided storage areas, the data storage area or the temporary storage area is allocated to the divided storage areas, upon receiving a data write request, the data storage area in which the write data is written and the segment are specified, the updated data is written in the temporary storage area included in the specified segment, the temporary storage area in which the data is written is set as a new data storage area, and data stored in the data storage area is erased and set as a new temporary storage area.