摘要:
First operations and second operations are performed in parallel. The first operations are operations to write first data to a first unit area which is any one of unit areas. The second operations are operations to read second data corresponding to the same logical page as first data from one or more flash memories and write the second data to a second unit area which is any one of the unit areas and different from the first unit area. Data transfer is performed between the first unit area and the second unit area so as to form data composed of the first data and a portion of the second data which is not replaced with the first data.