- minimize storage requirements
- minimize bandwidth requirements
- emphasize parallel (concurrent backups of different computers) performance to some extent
- allow expiration of old data that is no longer needed
- backshift's variable-length, content-based blocking algorithm. This makes python inspect every byte of the backup, one byte at a time.
- backshift's use of xz compression. xz packs files very hard, reducing storage and bandwidth requirements, but it is known to be slower than something like gzip that doesn't compress as well.