6. A non-transitory computer-readable storage medium having instructions stored therein, which when executed by a computer, cause the computer to perform operations for improving efficiency in a delta compression process, the operations comprising: selecting a data chunk to delta compress; selecting a data chunk to delta compress; generating a sketch for the selected data chunk; searching for a set of candidate data chunks using the sketch; ranking the set of candidate data chunks with at least minimum degree of similarity by location status data, wherein the location status data indicates a location and a compression status of a candidate data chunk status, wherein the location status data indicates the location and status of the candidate data chunk as in any one of a compressed in a cache status, a decompressed in a cache status, or a compressed in a data storage status, and wherein ranking the set of candidate data chunks using location status data for each candidate prefers a decompressed in a cache status over a compressed in a cache status; tie-breaking the set of candidates data chunks using degree of sketch similarity for each candidate; and delta compressing the selected data chunk with a selected candidate data chunk.
6. A non-transitory computer-readable storage medium having instructions stored therein, which when executed by a computer, cause the computer to perform operations for improving efficiency in a delta compression process, the operations comprising: selecting a data chunk to delta compress; selecting a data chunk to delta compress; generating a sketch for the selected data chunk; searching for a set of candidate data chunks using the sketch; ranking the set of candidate data chunks with at least minimum degree of similarity by location status data, wherein the location status data indicates a location and a compression status of a candidate data chunk status, wherein the location status data indicates the location and status of the candidate data chunk as in any one of a compressed in a cache status, a decompressed in a cache status, or a compressed in a data storage status, and wherein ranking the set of candidate data chunks using location status data for each candidate prefers a decompressed in a cache status over a compressed in a cache status; tie-breaking the set of candidates data chunks using degree of sketch similarity for each candidate; and delta compressing the selected data chunk with a selected candidate data chunk. 10. The non-transitory computer-readable storage medium of claim 6 , wherein ranking the set of candidate data chunks using location status data for each candidate orders the set of candidate data chunks based on access times to retrieve each candidate data chunk.