DIFFERENCE BACKUP SYSTEM, DIFFERENCE BACKUP METHOD AND PROGRAM

PROBLEM TO BE SOLVED: To provide a difference backup system for shortening the processing time of difference backup processing.SOLUTION: The difference backup system is configured to target a data section and file edition data having an edition history section. The difference backup system includes a block division section, an edition quantity measurement section, an edition quantity abstraction section, a change quantity calculation table creation section, a change quantity addition section, an abstraction classification unit change determination section, a block unit change determination section, a change unknown block number extraction section, a block comparison section and a difference backup execution section. The block comparison section does not perform comparison with respect to data on a block number having been determined to have a difference. Thus, it is possible to shorten the processing time of difference backup processing.