A storage system, upon receiving a marker from a host computer, executes a generation determination process for determining a generation of a first logical volume that is used by a host computer, and writes information related to the generation determined in this generation determination process to a physical storage device and/or a memory. A backup controller determines whether or not any data or a specified file and/or folder inside the first logical volume of the immediately preceding generation has changed, and when the result of this determination is affirmative, sends a marker insert indication, which induces the issuance of a marker, to the host computer, and when the result of the determination is negative, does not send the marker insert indication to the host computer.