Not so sure about the tar part, but the append-only nature is actually really well-known: look up log-structured filesystems, where all operations append to the

Not so sure about the tar part, but the append-only nature is actually really well-known: look up log-structured filesystems, where all operations append to the log and GC comes to clean up stale data later. I’m in the middle of writing a log-structured disk, and it’s really nice to work with. You get many things like clones, snapshots, etc for free. The replay problem is usually solved with periodic checkpoints of your map, and a checkpoint on shutdown. This way you only ever replay on failure, at which point performance doesn’t matter as much.