This invention relates to data backup and data recovery in a computer system. An outputting unit updates data stored in a first area based on an update request of data from the host computer, a creating unit stores update data for the update request in a second area, a marker processing unit creates a marker containing information of the range, in which the data is stored, and information indicating whether or not the data is allowed to be stored in a third area based on a request of creating the marker from the host computer to store the created marker in the second area, and a reflecting unit refers to the marker, obtains the update data corresponding to the data storing range, which is stored prior to the marker, and reflects the obtained update data to the third area.