I tried doing the whole OS on one drive, applications on another. I kind of doubt that it was any faster that way--I only did it to keep them separate from my OS drive since it used to get formatted fairly often. My current setup looks like this...
- Physical Drive 1: 80 gigs
- Logical Drive 1: 40 gigs, NTFS for windows, applications
- Logical Drive 2: 39 gigs, Ext3 for Linux, applications
- Logical Drive 3: 1 gig, Linux Swap
- Physical Drive 2: 80 gigs
- Logical Drive 1: 80 gigs, Ext3 for temporary storage
- Physical Drive 3: 300 gigs
- Logical Drive 1: 300 gigs, Ext3 for music
- Physical Drive 4: 200 gigs
- Logical Drive 1: 200 gigs, Ext3 for general storage
- Phyiscal Drive 5: 300 gigs
- Logical Drive 1: 300 gigs, Ext3 for general storage
- Phyiscal Drive 6: 160 gigs
- Logical Drive 1: 160 gigs, Ext3 for general storage
As you can see, I'm dual booting Linux and Windows right now, and I've got all of my storage drives formatted in Ext3 (which took a whole weekend a couple months ago). I'm not doing it here because I don't use Windows much, but it's definitely a good idea to give your Windows page file its own NTFS partition. I've yet to fool around with RAID arrays. They seem kind of wasteful outside of a dedicated server environment. If you've got the money, patience and real estate in your case though, go for it.
Jam it back in, in the dark.