"HDRFS is a lossless filesystem application which stores a complete history of every byte ever written to it. It is backed by a strictly append-only log, but works as a fully read/write POSIX-compatible filesystem. Think of it as a cross between a filesystem and tar, with infinite versioning and tuned to maximise ease of backups.

It is intended to be used by individuals to archive personal files."

Very half-baked. It works, but it turns out there are quite a few applications with highly pessimal write() patterns that bloat the metadata database, making it less general-purpose than I had hoped.