ULTRA_AMD :
The part where you say RAID 1 is not a backup, I beg to differ. RAID 1 is a mirroring array, the same data goes on both drives. If one drive fails the exact same data is on the other drive. This is a step in insuring your data. I have built a few mirroring array systems for small businesses and then a external hard drive or a zip drive to add a little more insurance.
Read his post again, he is absolutely correct. RAID is
not a substitute for backup. Yes, both RAID and backup protect your data, but do so in ways that protect from different failure modes.
RAID's primary purpose is availability - the ability to keep a server running during and throughout a storage system hardware failure. If a hard drive fails in a RAID-protected system, the system continues to run with the failed drive. Replacing the failed drive restores the redundancy, and the server keeps running throughout. This is the failure mode that RAID is designed to protect against.
A backup is not targeted at availability - if a server that is backed up but not in a RAID configuration goes down, it's down. No one can access it or it's services. Replace the failed component, and if that's the hard drive, then you restore your data from your backup. Now the server can be brought online again just like it was.
But backup can protect against many failure modes that RAID is ineffective against. If a virus infects your system and corrupts Windows to the point where the server won't boot, RAID doesn't help you. The second drive in the RAID 1 is a mirror - it's infected, too. If a user who's accessing the file server deletes a whole folder full of data on accident, guess what? It's deleted from the other RAID drive, too. RAID can't save you here. The only thing that can save you now is a backup.
Backup involves point-in-time snapshots of data. This means that you can restore data from backup that's a day old, a week old, a month old, etc. RAID is real-time -- there is no going back to old copies of data.
RAID also doesn't protect against a site catastrophe. If your building catches fire, your whole server is ruined, and the data along with it. If you have an off-site backup of the data, it's just a matter of calling your server vendor, ordering a new server, setting it up, and doing a restore. Back up and running.
So, do not confuse RAID and backup. They both play a part in protecting your data, but protect it from different things in different ways.