It seems that some people just love to learn the hard way.
Let's summarise the "laws of backup" :
(1) If its important, back it up to more than one device, typically the "rule of thumb" is that for anything critical, you should backup to minimum 3 independent devices, and preferably one of the devices is located at a different geographical location to your other backup devices and/or main computer.
(2) RAID MUST be considered to be ONE logical device. Therefore backing up to more than one device, as per rule number one, would mean multiple RAID devices. Trust me RAID is not infallible, I've seen lots of nasty corruption on RAID, hence RAID IS ONLY ONE DEVICE !
(3) Replace the word "RAID" in (2) with "cloud storage provider". Same rule. Don't put all your eggs in one basket.
(4) Test your backups regularly. An untested backup is NOT a backup. (and I mean manual human testing, not hitting the "verify" button in your software).
P.S. Added bonus... for those wondering "why minimum 3 copies" its called N+1 redundancy. If you only made two copies, you would be at N redundancy, which is fine ... until one of your backup devices fails. Then you're down to one, and you have no idea when that remaining device might fail. Therefore with N+1 redundancy (or three copies in laymans terms), you would be down to two working independent copies which buys you more safe time to fix the third.
