I keep clones and system images for the OS drive. I use a RAID 0 for media and a RAID 0 for exports and cache. My backup drive (internal) is not RAID, so that I can recover the files in any computer. I back up project files and new media as they are created.
All of my media is kept on external drives, both on and off location, and only copied as needed for projects in progress. I occasionally copy my work in progress to external drives and store them off location, rotating so as the latest copy is off location.
I backup System & software drive backup to a USB hard drive as a restorable image
The product I use is at http://www.terabyteunlimited.com/image-for-linux.htm
Image runs off of a bootable CD via Linux (the Zip you download includes a program to make the bootable CD) and it reads EVERYTHING on the drive, even the hidden registration information, so everything is restored when needed... and you may restore the image to a brand new drive in case of a crash, and not have to re-install anything