Others have mentioned rsync and I'd like to suggest on top of rdiff-backup but it's indeed for files, not partitions or disks. That being said IMHO if you are not managing data-centers and thus swapping entire physical disks by the bucket, you probably don't want to actually care for disks themselves.
If you genuinely have to frequently change not just data but entire systems, maybe looking at nix or cloud-init could help.