I know this might be a bit off topic but is it possible the backups cause the lag? I remember the last time the hard drives failed there was a few interesting post from Jorb explaining the lag problem and I might have completely misinterpreted what was said but it sounded as if there was a delay during the backups.
I don't consider myself an expert but just a suggestion. If the lag is caused by the backups. Would it not be possible to reduce the amount of lag by increasing the time between each backup?
The worst that might happen is that an hour of game play is lost on a failed hard drive. I mean if we only get 3 HD crashes a year it might be well worth losing a bit of game play for a less laggy game experience.
Of course if I'm completely wrong about the backups causing the server delays please feel free to ignore this post.
Edit: was referring to the OS upgrade thread.