zpaq

A journaling, incremental, deduplicating archiver

zpaq is a journaling, incremental, deduplicating archiver. "Journaling" means that when you update a file or directory, both the old and new versions are saved and can be extracted. "Incremental" means that only those files whose last-modified date has changed since the previous backup are added. For 100 GB of files, this typically takes 1-2 minutes, vs. a few hours to create the first version. "Deduplicating" means that identical files or fragments are stored only once to save time and space.