A few highlights (for me at least):
- They have implemented support for object locking and versioning to prevent a compromised set of S3 keys being used to erase backups. There seems to be a pull request outstanding to dynamically shift forward the compliance hold each time an object file is "deemed still used", but very few s3 bucket based backup tools seem to really think about resisting deletion and documenting best practice. I like to use minimum privilege and deny DeleteObject permission, but using versioning and object locking policies seems to be an interesting potential solution.
- Inclusion of (optional) Reed Solomon error correction codes in backup objects.
- a CLI verification option that will test a given % of your backup objects (at random) every time it's run, to give you opportunistic random verification to try find issues.
- reasonably well documented CLI options for recovering data were anything to go wrong - as the developers mention, there are a wide range of ways to recover data. Interestingly, they appear to have actually implemented these, rather than leave them as theoretical. For example, CLI commands to interact with indexes, manifests, blobs, snapshots, etc. You don't need them normally, but having these available lets you look around a simple backup and understand the format and gain confidence in it, and that the tools work.
The only feature it seems to me to be lacking is asymmetric encryption of backups, so you can keep the key needed for recovery away from the host you are backing up.