Suggestions for Backup of My MacPro

I've had my Mac Pro sense April and I'm really glad I made the switch. I've been lazy about backing up my data etc. but it's time to get serious. Here's my question.

I know I can burn data to a CD but I would prefer to back up to another hard drive. I see my options as follows. What do you folks suggest.

1) Install an additional drive in the open bay and use it for backup and / or additional storage.

2) Use a Firewire 400 or 800 external drive for backup.

Your thoughts?

Thanks.

Go with an external drive. Even better, go with two external drives and rotate your backups. This is what I do. I have two external drives. Each time I backup, I take the new backup to work and keep it there and bring the old backup home. This way, my newest backup is always "off site". With two backups, you have two physically separated locations with your data at them... sort of a geo redundant backup. Short of a huge New Orleans style calamity, your data will survive no matter what happens to your home or your office. They would both have to be wiped out together to lose everything.

With a lifetime of family and other photos now stored exclusively digitally, "survivability" of my personal data is really important. So, I chose a two site, rotating backup strategy. I would recommend the same for just about anyone who can afford the two drives. One backup is better than none, but two is significantly better than just one.