I would like some advice on backing up. Should I have two separate HDs. one with time machine on,it and the other with Superduper on it. Or one HD with two partitions on it and both backups on
It depends on how much you value your data. Two drives would give you less chance of drive failure causing a problem, but as a backup is just that and for emergencies, then the chance of losing your internal drive and even one external drive at the same time is pretty remote. For what it's worth, I use your second suggestion.
You haven't asked about drive size but I'll put in my two-pennyworth! Lots of people will tell you you need a drive at least the size of your internal for a clone and bigger by about 50% for Time Machine. I work on the amount of data I have instead. For example, I have a 250GB drive in my machine which after 4 years has acquired 110GB of data. I can't see me filling the other 140GB in the near future. So, for my clone I've allowed 200GB which is all but double my current data but less than the disc size. The Time Machine partition (on a 500GB drive) is therefore 300GB and, bearing in mind I use my machine for business so a lot more than most people, TM still has room for the last 15 months of data.
I don't see a real need for both SD and TM backups other than the reason I have both. You can populate a new drive by starting from your install disc and restoring from TM but, for me, the time taken to buy and install a replacement drive could be more costly than the drive itself so, if I have drive failure, I can instantly start from my "always bang up to date"( yeah, right!) SD clone and carry on working until I have my new drive up and running when I'd clone back from the external i.e. no time loss.
Please note that the sizes quoted are approximate - although you buy a drive as 500GB you don't get 500GB you can use.
Douglas Cheney 