Backing up to hard drives is good. Backing up to removable harddrives is better (the combination removable tray and hard drive is called "media"). But backing up to RAIDED media is the best! presently, the only company I know of which makes RAIDED media is http://www.high-rely.com. They offer a 3 drive RAID 5 media and a two drive RAID 1 (mirror) media as well as RAID 0 media. They also offer "Softwareless backup". Pretty cool stuff. Bit pricey.