Mirrored Raid as Backup Solution

Nope this is not how RAID works.

RAID 0 is for performance.
RAID 1 & 5 is some performance gains, and it also keeps a system up and running if a disk fails.

 

Raid 3 (byte level) and 4 (block level) provide a parity disk with a copy of all the data striped across the other disks in the array.

Raid 3:
http://www.pcguide.com/ref/hdd/perf/raid/levels/singleLevel3-c.html

Raid 4:
http://www.pcguide.com/ref/hdd/perf/raid/levels/singleLevel3-c.html

Downside: you'll need a hardware RAID system to do it, it can't be done with software RAID.

Edit: seeing that you have only 2 drives, you can't do RAID 3 or 4, but if you ever have more drives, it's a very safe system.

 

Raid != Backup.

If you do a RAID 1 mirror you may NOT turn off or disconnect your second drive. A Mirror RAID protects you against hard drive mechanical failure, that is all. If you accidentally delete a crititcal file, or munge your OS with a software install, or overwrite a good file with a bad one of the same name, the damage is done immediately to the mirror as well as to the main drive.

You don't want a RAID. What you really want is a periodic backup, perhaps which you can schedule. Look at Retrospect (commercial), Silverkeeper (shareware) or other programs that can do a backup or a sync between volumes. www.versiontracker.com

Note: why all of a sudden all the threads confusing RAID with backup??

 

I'm guessing that it's all the marketing that we've seen lately on external SATA boxes. Look at that, then scan quickly over some vague RAID info - mirror!! backup!! I get it, I need a RAID! Only geeks read the details...

Good news is, this all comes at a time when HD is blossoming and more people may really be in need of a RAID...