Stripe Your Boot Disk
As part of my attempt to fix my broken Mac Pro, I ended up reinstalling the operating system on a new hard disk. Actually, what I ended up doing was taking two smaller disks (160GB each) and making them into a striped RAID set. When I had just the one drive, the super fast Mac Pro with it's 4 processors and 3GB of RAM was quite often bottlenecking on reading application images off the disk. So if I wanted to start two things at once, like Mail and Firefox, or three things, like Mail, Firefox and Adium, it would take forever. Just as long as it took on my 3+ year old G5.
Anyway, it turns out this make a huge difference, not surprisingly. Everything starts way faster, and the machine boots faster too. So if you have the time, and two identical drives, you should try it. Here's how:
Put the new disks in. Keep the old disk in there so you can copy your home directory over to it later.
Boot with the install disk. Hold down the "C" key after powering on.
When the Installer comes up, select Tools -> Disk Utility. Use Disk Utility to create a RAID set. You want striped, so the new virtual disk is the size of the two individual disks together. I recommend naming the virtual disk something other than "Macintosh HD" so you can distinguish it from your other, existing disk.
Create a journaled file system on the new RAID set.
Exit disk utility.
Now install the operating system, and select your new RAID set as the target. After you get booted back up, copy all your files and applications from the old disk to the same places in the new disk. You'll be burning up the road from then on.