Patent ID: 7437603
Filing Date: 2008-10-14
Classification: G06F

Abstract:
1. A method for storing a snapshot, which causes a storage system to execute restoring processing by overwriting a primary volume with data of a snapshot volume, the storage system comprising: the primary volume for storing data to be accessed by a client computer; the snapshot volume for holding a snapshot of the primary volume; and a differential volume for storing differential data between the primary volume and the snapshot volume, the method comprising the steps of: causing the storage system to receive a restoring starting command containing a restoring source snapshot volume from a management computer; referring to a differential block management unit presetting in which of data blocks of the differential volume and the primary volume a data block of the restoring source snapshot volume is present based on the received restoring starting command to determine which of the primary volume and the differential volume a volume storing real data is for a restoring target data block; copying data stored in the data block of the differential volume indicated by the differential block management unit to the data block of the primary volume to execute restoring when the restoring target data block is in the differential volume; receiving a request of accessing the primary volume from the client computer while restoring; switching to accessing to a virtual primary volume which provides a volume image after restoration where data of the primary volume and data of the differential volume are combined together based on the snapshot volume; and executing the accessing request from the client computer to the virtual primary volume.