 Data that is already stored efficiently may not allow "any" significant compression; a sparse database may offer much larger factors.Software compression can achieve much better results with sparse data, but uses the host computer's processor, and can slow the backup if it is unable to compress as fast as the data is written.The compression algorithms used in low-end products are not the most effective known today, and better results can usually be obtained by turning off hardware compression AND using software compression (and encryption if desired) instead.