Patent ID: 6594744
Filing Date: 2003-07-15
Classification: G06F,Y10S

Abstract:
A method of managing a snapshot volume and a base volume for data storage in a computer storage device, wherein the snapshot volume is formed from the base volume using a single snapshot repository, the base volume storing first data in base data blocks before the snapshot volume is created and storing second data in the base data blocks after the snapshot volume is created, the snapshot volume representing a state of the first data in the base volume at a point in time when the snapshot volume is created, the snapshot repository containing repository data blocks and the snapshot repository storing in the repository data blocks the first data copied from the base volume upon storing the second data in the base volume, the method comprising the steps of:creating the snapshot volume at a first point in time; forming the snapshot repository; starting a first image in the snapshot repository at the first point in time, the first image containing the repository data blocks; linking the snapshot volume to the base volume and to the first image in the snapshot repository, the base data blocks in the base volume containing portions of the first data that have not been copied to the snapshot repository and the repository data blocks in the snapshot repository containing portions of the first data that have been copied to the snapshot repository; starting a second image in the snapshot repository at a second point in time, the second image containing the repository data blocks that contain the first data copied from the base volume after starting the second image, the starting of the second image effectively stopping the first image in the snapshot repository at the second point in time; and linking the snapshot volume also to the second image in the snapshot repository.