You can do that with ZFS at the cost of defining separate filesystems per directory. I don't use multiple replicas, but I use that to tailor my backups per dir

You can do that with ZFS at the cost of defining separate filesystems per directory. I don't use multiple replicas, but I use that to tailor my backups per directory. ~/documents is snapshotted and backed up on the regular, with long-lived snapshots. Code is snapshotted regularly, but snapshots don't live too long, and they're not shipped to a different drive. I don't care for ~/tmp so no snapshots. --- edit: the cost, besides having to actually create the file systems, is that moving data between them isn't instant.