Edelta: A Word-Enlarging Based Fast Delta Compression Approach

Delta compression, a promising data reduction approach capable of finding the small differences (i.e., delta) among very similar files and chunks, is widely used for optimizing replicate synchronization, backup/archival storage, cache compression, etc. However, delta compression is costly because of its time-consuming wordmatching operations for delta calculation. Our indepth examination suggests that there exists strong wordcontent locality for delta compression, which means that contiguous duplicate words appear in approximately the same order in their similar versions. This observation motivates us to propose Edelta, a fast delta compression approach based on a word-enlarging process that exploits word-content locality. Specifically, Edelta will first tentatively find a matched (duplicate) word, and then greedily stretch the matched word boundary to find a likely much longer (enlarged) duplicate word. Hence, Edelta effectively reduces a potentially large number of the traditional time-consuming word-matching operations to a single word-enlarging operation, which significantly accelerates the delta compression process. Our evaluation based on two case studies shows that Edelta achieves an encoding speedup of 3X∼10X over the state-of-the-art Ddelta, Xdelta, and Zdelta approaches without noticeably sacrificing the compression ratio.