Patent ID: 6061770
Filing Date: 2000-05-09
Classification: G06F

Abstract:
A computer system having a read/write container with locations for storage of blocks of read/write on-line data, said system further comprising a backup structure for backing up the on-line data at a instant in time, said backup structure comprising:means for creating a backing store container that is smaller than the read/write container;means for copying to the backing store container from the read/write container an unmodified copy of each block of on-line data that is to be modified subsequent to a predetermined snapshot time;a mapping structure that maps the blocks of data in the backing store container with locations in the read-write container from which the blocks were copied;means for converting a physical block number of a block of data in the read-write container to a virtual block number in the backing store container;means for creating and storing a first level table in memory and in the backing store container;means for creating and storing a second level table in the backing store container, said second level table storing a block of data that is copied from the read/write container to the backing store container;means for accessing the first and second level tables in the backing store container using the virtual block number; andmeans for storing a beginning block number of the second level table in a first level table entry.