If you just want a reasonably small (1-4tb) volume with redundancy and don't care too much about performance, you could buy 2x raspberry pi 4 and those cheap en

If you just want a reasonably small (1-4tb) volume with redundancy and don't care too much about performance, you could buy 2x raspberry pi 4 and those cheap enclosures that provides space for a hard disk (usb 3.0). One is the primary, the other is the backup. Schedule an rsync from the primary. This would be cheap and simple. It also lets you undo an accidental "rm -f" before the next scheduled rsync.