The device controller (a) executes a data I/O process with respect to a physical storage area in accordance with an I/O command, and (b) sends to the storage controller an I/O command-related response comprising status information subsequent to being changed in accordance with the I/O process. The storage controller (A) receives the response from the target physical storage device, and (B) based on the status information included in the response received in (A), makes a determination as to whether or not to execute internal processing, and in a case where the result of the determination is to execute internal processing, sends to the target physical storage device an internal processing execution command instructing the execution of internal processing. The device controller in the target physical storage device (c), upon receiving the internal processing execution command, executes internal processing in accordance with the internal processing execution command.