Are all external hard drives the same?

Reliability is the thing I would worry about the most.

I've run the Seagate 1.5 and 2 Gb USB drives from BEst Buy for a few years now and have found them to be most reliable and essentially trouble free. They also come with backup software installed which has also been very reliable and trouble free. I see no reason to look elsewhere, there is some motor noise when they first fire up, but nothing of much consequence there really.

Highly recommended.

Whoops, I meant Tb, not Gb above.

Sorry.

RAID technology in a single storage device provides storage redundancy to provide high or constant availability in teh case of certain hardware failures.

Its good stuff but not a good fit for most home users IMHO. Having a physical backup drive is the single best protection for home use. Having a backup at a separate location from the main is the best solution in case fire or other localized disaster is a concern.

If a main fails, the backup can be switched in easily with some but little downtime. Most business applications that use RAID cannot afford ANY down time.

To accomplish that, data is replicated or backed up to additional devices that can be switched in quickly if needed.

RAID alone adds cost and little value for a home user.