Patent ID: 7103713
Filing Date: 2006-09-05
Classification: G06F

Abstract:
1. A storage system, comprising a primary disk subsystem having a disk drive provided for normal operation, a first file server that controls input and output of data to/from the primary disk subsystem, a secondary disk subsystem having a disk drive that stores a duplicate of data stored in the primary disk subsystem, a second file server that controls input and output of data to/from the secondary disk subsystem, and a communications line that connects the primary disk subsystem and the secondary disk subsystem, the primary disk subsystem comprising a primary volume where normal reading and writing are performed, a first differential volume that is arranged to store differential data of a snapshot of the primary volume, a first management information holding module that manages the differential data in the primary volume, and a first data transfer module that transfers data to the secondary disk subsystem, the secondary disk subsystem comprising a secondary volume that stores a duplicate of the data stored in the primary volume, a second differential volume that is arranged to store differential data of a snapshot of the secondary volume, a second management information holding module that manages the differential data in the secondary volume, and a second data transfer module that transfers data to the primary disk subsystem, the first file server and the second file server each comprising a host input/output control module that sends and receives data and a control signal to/from a host, a disk input/output control module that transfers data and a control signal between the primary disk subsystem and secondary disk subsystem, a cache memory that temporarily stores data sent and received to/from the host input/output control module and the disk input/output control module, a CPU that controls operations of the first file server and second file server by executing a control program, and a memory where the control program is stored, wherein: the first data transfer module collectively sends update data to be written into the primary volume, an update address in the primary volume where the update data is to be written, differential data stored at the update address in the primary volume, and management information including a storage address in the first differential volume for the differential data, to the second data transfer module; the second data transfer module: stores the update data sent from the first data transfer module to an update address in the secondary volume; stores the differential data sent from the first data transfer module to the second differential volume; updates the second management information holding module based on the management information sent from the first data transfer module; and then informs completion of data updating to the first data transfer module; and the first data transfer module: when the information of completion of the data updating is received from the second data transfer module: stores the update data to the update address in the primary volume; stores the differential data stored at the update address in the primary volume, into the storage address of the first differential volume; and updates the first management information holding module.