Patent 7512756 was granted and assigned to RELDATA on March, 2009 by the United States Patent and Trademark Office.
The portion of a source block storage resource to be replicated, and the corresponding portion of the block storage resource being written to, are each divided into a predefined number of equal-sized spans. A digest calculation is then generated for each span in a corresponding pair and compared. If the digests do not match, those spans are divided into still smaller spans, and digests are calculated and compare iteratively, to identify smaller areas of discrepancies and reduce the number of blocks that are actually written.