The idea is:
The latest backup (timestamped) always contains a full copy of the current source state.
Any previous backups are stored as deltas: files that were deleted or modified compared to the next (newer) version.
There are no version numbers — just timestamps. New versions can be inserted naturally.
Each time you back up:
1. Compare the current source with the latest backup.
2. For files that changed or were deleted: move them into a new delta folder (timestamped).
3. For new/changed files: copy them into the latest snapshot folder (only as needed).
4. Optionally rotate old deltas to keep history manageable.
This means:
The latest backup is always a usable full snapshot (fast restore).
Previous versions can be reconstructed by applying reverse deltas.
If the source is intact, the system self-heals: corrupted backups are replaced on the next run.
Only one full copy is needed, like a versioned rsync mirror.
As time goes by, losing old versions is low-impact.
It's user friendly since the latest backup can be browsed through with regular file explorers.
Example:
Initial backup:
latest/ a.txt # "Hello" b.txt # "World"
Next day, a.txt is changed and b.txt is deleted:
latest/ a.txt # "Hi" backup-2024-06-27T14:00:00/ a.txt # "Hello" b.txt # "World"
The newest version is always in latest/, and previous versions can be reconstructed by applying the deltas in reverse.
I'm curious: has this been done before under another name? Are there edge cases I’m overlooking that make it impractical in real-world tools?
Would love your thoughts.
It is not clear what problem with existing backup strategies this solves.
I mean you can use a traditional delta backup tool and make one full copy of the current data separately with less chance for errors.
It seems too clever by half and it is not clear to me from the question what problem it solves. Good luck.