Snapshotting sparse data is much faster thanks to new repository format where compression is performed after hashing, so zero data is only compressed once:
So is append-only mode already possible or the new index format allows to implement it later?
I guess to enable it now, we would need to disable full maintenance.
Kopia still uses deletes in one or two places, those will be eradicated in v0.10 but the primary index structure is now append-only (does not require deletes for performance, but will attempt them for cleanliness).
The UX of maintenance in append-only cases still needs to be worked out, that’s why I’m not claiming append-only is possible today.