This thread has made me rethink my backup strategy... currently I stick the disk in and make a backup when I'm about to go and see my mum, but this means that if I had a catastrophic failure on that same day the backup at her place would be getting quite stale (eg on a 2 week cycle the backup would be 4 weeks old)
Instead I'm going to set it up so that the drive stays in and powered on 24/7, then the contents of the NAS box are rsync'd at least once per day to the drive. This means if the NAS toasts itself I'll still have the single drive as a current backup. If there's a fire or some other event which destroys my rack of equipment then all bets are off, it's back to the stale backup.
