The rationale is mostly valid. The slowest part of the computer is moving the heads around on the platter to find different data that might be needed. Having OS, Apps, Swap, and Working Data all on separate volumes will reduce the need to move individual heads around, making for an overall faster machine. But this is not easy to do, and the improvements are small unless you're really pushing the machine's limits. Most casual users will likely NOT see a worthwhile benefit, and I guarantee you that you will have troubles with non-standard configurations.
Before doing anything to "optimize" the disk layout, make sure you have as much physical memory as possible. 4GB in a 32 bit system is not too big, and 8 GB in a 64 bit system is dandy. The days of 1GB and less memory systems are long gone. Win 7's caching mechanisms will do a lot to keep data at hand and minimize disk access. Any time Win can avoid the disk it will, and that is a clear hit in the performance column.
If you can place everything as drive C: on a very fast hardware RAID 5 volume, that will be the best general purpose configuration for most uses.
There really is no one best configuration. The best configuration will depend on many things, from OS choices, to how you are using the machine. For my own use, where I use my machine heavily for video processing, and use Win XP, I would go with something like this:
Drive C: I would buy the largest, fastest single Hard Drive I can find. Speed is more important than size, but generally speaking larger drives are faster, and size must merely be sufficient to hold the OS and applications, plus your "My Documents" tree.
Drive D: I would configure a RAID 5 Array of the largest and fastest set of drives I could find. Minimum of 3 drives, up to 5 preferred. Hardware RAID controllers preferred, but Software Raid could be used at some sacrifice in performance. I have used Software Raid volumes with good success. This would hold the working data, the video files being processed, etc.
Drive Z: The smallest, fastest drive I can find. This need only hold the swap file. Benefits of moving the swap file to a dedicated drive are real. But in some cases (Vista, Win 7) if you have sufficient memory, you may chose to drop a swap file entirely, in which case you do not need Drive Z. This is controversial, and you risk a BSOD on running out of memory, but I have used it quite successfully.
You could also move the Programs (Apps) directory to a separate drive, for a very small improvement, but this is a pain in the behind to make work properly and generally only gives a small improvement. But if you can tweak the windows registry to move "Program Files" to another drive, and want yet another drive in the system, then it will give you some slightly noticeable improvement.
Ditto for the My Documents tree, which can be tweaked to be on a separate volume, but likewise probably more trouble than it's worth.
But the major caveat is simply that modern disks are already very fast, and few users really stress the limits of the hardware they have. Going to such complications will cost you time, hair-pulling, and money, and may well not give a significant improvement in your individual performance.
Unless you have done benchmark studies that clearly show bottlenecks in I/O slowing down your processing, I would suggest simply putting in the fastest C: drive you can (either a single drive, or if you must, Raid) and forgetting about it. Large heavily loaded servers and database machines may be worth the effort. Desktops usually are not, except in specialized cases such as heavy-duty video transcoding, etc. Going to such extremes because you "think" you know where the bottlenecks are will result in disappointment, I guarantee it. Throwing hardware at a system that has not been properly measured is neither science nor engineering.
SSD drives are the high-tech darling in the eyes of many performance enthusiasts, but they are expensive and tend to be on the small side, and long term reliability may be in doubt. Still they can in some cases be very very fast. Perhaps an SSD for the OS volume might be a way to go. Maybe. But I'd bet it would give less performance improvement than you might expect.
My advice is to get a main drive(s) of:
1) WD Velociraptor (300GB), or
2) WD 1TB Black, or
3) WD 1TB Black in RAID0 (I'm not a big fan of RAID0, but feel free to read up on it)
It's also important to have enough RAM so that Windows buffers programs instead of going to the hard drive. 4GB is optimal (need a 64bit OS). For 32-bit, install at least 2GB; you can't see more than about 3GB so the most you should install is 3GB.
Only loading times for new levels are affected and this is proportional to the READ SPEED for the drive.
A good SSD makes the Windows interface much more responsive. You can decide how much you want to pay for that luxury. My recommendation to most people is to:
- stick with a fast hard drive for now (WD Velociraptor is still a great drive)
- don't worry about putting Windows on one drive and applications on another. You might see some small improvement but it's not worth the expense and noise plus you'd be better off adding more RAM (again, 4GB is optimal for x64 OS)
- have sufficient RAM
- buy an SSD in another year or more when quality, speed etc have improved and prices drop
Choose 2 hard disk RAID 0 (Western Digital Black Caviar) 320Gb, 1Tb or 1.5Tb for storage, the rest is external hdd. RAM minimum is 4Gb. Make sure you have healthy cooling in your system. This is my basic configuration.