I tried out Mozy as a solution for online backups about a year ago. Perhaps it’s improved since then but at the time it stunk. It would error out all the time, it took me almost 2 months to create the first backup (even though I had it on all the time and my connection was plenty fast), and so I just gave up.
I just signed up for Carbonite and as far as performance goes it is much better than Mozy was. The only issue is that Carbonite doesn’t back up external drives. If that external drive were an internal hard drive then it would back it up, but because it’s external it won’t. Of course there’s logic to this, since people could hook up several terabytes of external drives to one computer and that would ruin Carbonite’s business model, but honestly, how many people would do that? Sure, I’ve got about 300 GB that I want to back up, but I think I’m one of the exceptions. I would guess 90% of people don’t have more than 10-20 GB that they want to back up. Of course that will increase over time, but the price of storage and bandwidth will drop at the same time.
Carbonite’s CEO has said they’re coming out with a Plus plan that will allow external hard drives to be backed up, but it seems like this is a major hole in their current model. If I was aware of another online backup service that would allow me to back up my external drive (all other things being equal) I’d switch in a heartbeat.