best way to have multiple homes?

I have a number of drives on a given machine with different disk configuration. - root drive. - 2 disk mirror. - zfs array. To accommodate a variety of failure scenarios, I want user homes to be: - zfs when it's up and working. /mypool/mydataset/home/username - mirror if zfs is down but mdadm is working. /mymirror/home/username - root drive if there's something wrong with both zfs and mdadm. /home/username Files will need to be synced across all 3. What's the best way to achieve this? Best in terms of reliability: 1. fault tolerant (works even when some software or hardware is broken - i.e. the more faults it will tolerate, the better. ideally will "just work" with cpu/ram/mb/boot drive working and everything else is broken, including nic, vga card, all other hdds, etc; while being transplantable to new cpu/ram/mb/boot drive to accommodate those failures) 2. tamper proof - users can't stuff it up to remove this "protection".