Patent ID: 8327095
Filing Date: 2012-12-04
Classification: G06F

Abstract:
1. A method, comprising: maintaining information on a source volume having a plurality of data units and a plurality of target volumes created at different points-in-time; maintaining a logical copy of the data units in the source volume for the different points-in-time; generating a different source downstream pointer for each data unit in the source volume to point to a corresponding data unit in a first target volume, wherein there are a plurality of the source downstream pointers for the data units in the source volume; generating, for each target volume data unit whose data is maintained in the source volume or another one of the target volumes, a different first upstream pointer indicating one of the source and target volumes from which the target volume data unit inherits data, wherein there are a plurality of the first downstream pointers for the data units in the target volume; generating, for each target volume data unit whose data is maintained in the source volume or another one of the target volumes, a different second upstream pointer indicating one of the source and target volumes having the data for the data unit, wherein there are a plurality of the second upstream pointers for the data units in the target volume; creating a new target volume as a logical copy of the source volume; and updating the first upstream pointers of the first target volume data units to point to the new target volume, wherein the second upstream pointers of the first target volume data units point to the source volume data units while the first upstream pointers of the first target volume data units point to the new target volume.