Patent ID: 7100089
Filing Date: 2006-08-29
Classification: G06F

Abstract:
1. A method for determining differences between two snapshots of a base volume in a snapshot tree comprising the base volume and a plurality of snapshot volumes, wherein each of the two snapshots corresponds to a respective snapshot volume of the snapshot tree, wherein the snapshot volumes corresponding to the two snapshots are in a same branch of the snapshot tree, the method beginning with the older and ending with the more recent of the snapshot volumes corresponding to the two snapshots, the method comprising for each snapshot volume: searching for exceptions in exception tables of the snapshot volume presently being considered, wherein the exceptions tables only point to data that were (1) originally in the base volume at a time the snapshot volume presently being considered was taken and (2) later modified after the snapshot volume presently being considered was taken; if exceptions are found, processing for the exceptions; otherwise, if no exceptions are found, determining whether the snapshot volume presently being considered is the more recent of the snapshot volumes corresponding to the two snapshots; and if the snapshot volume presently being considered is not the more recent of the snapshot volumes corresponding to the two snapshots, moving to the next snapshot volume up the branch from the snapshot volume presently being considered and treating the next snapshot volume as the snapshot presently being considered.