Btw, we all have our source in git or mercurial (vcs with full history) with an offsite repo, right? also, RAID isn't a backup. How many lessons do people need to keep relearning?
Let me repeat: "Keeping anything important in one place is a bad idea"
http://serverfault.com/questions/2888/why-is-raid-not-a-back...
But backup is a separate copy of your data set aside for emergencies, while raid just increases the reliability of your one, in use, copy of the data.
Heres an example: You just accidentally dropped a table from your database. Can you recover it with a backup? Can you recover it with RAID?
If its music/movies it's not that big an issue to get 1 corrupted file, on the other hand, corruption on critical work files could be a disaster.
I say RAID is fine for a media NAS box, but for critical business files, a more thorough backup strategy is required...
In that case I still wouldn't call it a backup. I'd just say that the array itself was failure-resistant enough that you've chosen not to maintain a backup.