I second drive mirroring with ZFS. Truenas Scale has been a quantum leap for me. I have two very old Dell T110 with 32GB ram each. One, the main one, has 4x 4GB Western Digital Gold drives, which cost me a fortune at the time. I think they are in raid5 but cant remember. The other t110 has cheaper WD reds. I turn on the slave machine on saturdays to complete replication tasks. I dont have a robust backup model yet besides replicating to an external HD on a 3rd machine but will need to work on that.