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.
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edit: the cost, besides having to actually create the file systems, is that moving data between them isn't instant.
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.
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edit: the cost, besides having to actually create the file systems, is that moving data between them isn't instant.