It is detected whether write data has been correctly transmitted to a storage device under a protocol for directly connecting the storage device to a processor. An information processing system including: a processor; a memory; and a storage device, the processor first transmitting to the storage device, a command to invalidate data in a data area and which is designated by a write command, the storage device invalidating the data, the processor second transmitting to the storage device, the write command to write the data into the data area, and the storage device writing the data into the data area in accordance with the write command, validating the data in a data area into which the storage device has been successful in writing the data, and maintaining the data invalidated in a data area into which the storage device has failed in writing the data.