I am not very knowledgeable when it comes about what a software developer needs from his/her computer, my only programming experience is using C++ and Turbo Pascal for a few semesters around 9 years ago and I am sure things have changed plenty in the mean time.
If most of the time you are using applications that are reading and writing large chunks of data the 7200 RPM drive may be the best choice for you. However if storage is more of an issue for you the dual 5400 RPM drives may be the way to go. It really all depends on your needs.
I would go with the dual HDD set up for 2 reasons. First, the laptop my company got me for use at home and on the road has a 7200 RPM drive, and for what I do I haven’t noticed any significant performance increases over 5400 RPM HDDs I have used in the past. However, this may be because the applications I use and/or the type of computing I do may not really see any benefit from the faster drives while people using other applications may really benefit from a 7200 RPM drive. Secondly, I have yet to see any conclusive data that proves a faster hard drive is substantially more valuable to system performance. From all the discussions and articles I have read it seems like you’ll find 10 people who think a faster drive makes a huge difference and 10 people who think it makes a nominal difference.
Since I haven’t seen any significant benefit from a 7200 RPM drive I’ll be ordering a dv9000 with dual 80GB drives. For my needs spending $139 for dual, 5400 RPM, 80GB drives makes more sense than spending $116 for a single 100 GB, 7200 RPM drive. I need storage more than the nominal performance increase I am personally seeing from the 7200 RPM drive.
However, if you know for a fact that the 7200RPM drive is going to provide you with a measurable performance increase I would suggest you go with that option.
Here’s an interesting article on 4200RPM, 5400 RPM and 7200RPM drives that has much better technical information than I could ever give. It’s from December 2004 so it may be out of date, but I think the general principal still holds true.
http://www.powernotebooks.com/articl...=fullnews&id=5
I have never mirrored my drive. But for the amount and type of software I use it’s not particularly valuable for me. I keep the amount of software on my machines down to what is absolutely necessary, with just a handful of ancillary programs, and I back up all of my important data religiously. So if I do have a crash I just need to use the recovery discs, or reinstall my OS, and other programs, and it wouldn’t take very long to get my machine back to where it was. But if you have loads and loads of programs, and custom skins, or other things that would make it very time consuming or difficult for you to get your notebook back to where it was mirroring would probably be a good choice for you.
I don’t think it’s a good idea to mirror or backup to a drive that’s on your notebook though. It would help if one drive crashed, but let’s say you dropped your notebook or spilled or it was somehow damaged, there’s no way that you can be sure the hard drive containing the mirror would remain undamaged. I think any type of backup would be best done to an external drive or desktop.
With everything right like you left it BEFORE the data loss.
The below is a repost I just made in another thread, hope it helps someone: 
