So I've got two 500GB HDs...

[Fyron]

You do not need a 3rd drive to do RAID; just set up RAID 1 (never RAID 0) so all data is mirrored between the drives. If one drive kicks the bucket, all data is still there on the other. You get a bit of a write penalty and a read gain, but the main benefit is the fault tolerance. Since the whole point of the second drive was backup anyways, losing access to half the total storage space shouldn't be an issue. RAID 1 will do a far better job of backing up data than you could ever do manually. Automation is the key to backups.

Yes, it is technically better to use RAID 3 or 5 in terms of lost percent of storage space, but its not strictly necessary for a desktop computer. A media center would be better off with more drives and a higher RAID level, due to all the massive movie files, but you aren't doing that I think.

[AstralWanderer]

Fyron said:
You do not need a 3rd drive to do RAID; just set up RAID 1 (never RAID 0) so all data is mirrored between the drives. If one drive kicks the bucket, all data is still there on the other. You get a bit of a write penalty and a read gain, but the main benefit is the fault tolerance. Since the whole point of the second drive was backup anyways, losing access to half the total storage space shouldn't be an issue. RAID 1 will do a far better job of backing up data than you could ever do manually. Automation is the key to backups.

For a home user, mirroring is likely to be overkill and it only covers hard drive failure. For situations like a messed-up configuration or serious malware infection, mirroring would not help at all, since the copy would have the exact same problem. A regular (weekly or so) disk image backup (using software like Drive Snapshot or Acronis TrueImage (both of which can make backups of system partitions in the background and can be automated via Task Manager) would likely serve better and these could be done to the 160GB disk initially.