This is the problem I have been contemplating lately as well.
I have over 600GB of data altogether, which includes approximately 25GB of documents and photos, 150GB of music, and another 400GB or so of movies. Right now, I run a nightly backup of all my critical data, plus the music, since that is about as much as I can fit on my 200GB external hard drive. This backup is merely a straight incremental copy of all my data, so any corrupted files that are not caught within a day will surely get copied to the backup drive. However, a few corrupt files is not nerely as important to me as an all out drive failure.
I've always figured that an external hard drive was the best backup solution since it allows me to have one good copy of my data at any given time. If my internal hard drives fail, I can use the external drive. Conversely, if the external drive fails, the internal drives should last enough time for me to acquire another external drive and resume all backups. It's not a fail safe solution like a business would use, but it works for my needs... or so I thought.
Recently, I've been considering the loopholes of this backup procedure. For example, if there was ever a sever power surge or disruption in my building with the ability to impair electronic devices, it's probable that both my internal and external hard drives would be toast. So, what's the best solution?
I've been thinking about using both an external hard drive for nightly backups along with weekly DVD backups, and creating permanent archives of my music and movies. However, this is a somewhat daunting solution, since I will have to burn all the discs and track their contents.
So, what's the best solution, taking into consideration the amount of effor that would be needed to complete backups? Multiple external drives that are rotated on a weekly basis to avoid simultaneous failure? Using both an external hard drive and DVDs?
It's confusing 
