Patent ID: 7293068
Filing Date: 2007-11-06
Classification: G06F

Abstract:
1. A data duplicating method that connects a first information processing system comprised of a first host computer and a first storage device and at least one second information processing system comprised of a second host computer and a second storage device through a data transfer path and copies first update data generated in said first information processing system to said second information processing system, wherein said first information processing system generates first difference control information for identifying any said first update data not copied to the second information processing system, wherein said second information processing system generates second difference control information for identifying second update data generated in said second information processing system after taking over information and data processing performed by said first information processing system when said first information processing system stops operating, and after resumption of operation of said first information processing system, the second information processing system reads the first difference information and executes a logical sum operation on the first difference information and the second difference information managed in the second information processing system, a result of the logical sum operation being reflected in the second difference control information, said second update data being selectively copied to said first information processing system on the basis of said second difference control information in which said logical sum is reflected, wherein said difference control information is a bit map that indicates the presence or absence of completion of data duplication of first and second update data at a plurality of individual units of data storage in each of said first and second storage devices.