As Chris mentioned on his blog - we have a new paper out that talks about Optimizing Storage for Exchange Server 2003.

Definitely a good read that talks about where Exchange generates most IO, what the best practices are for placing Exchange files on different types of storage and, very importantly, how storage capacity and performance efficiency do not always have to go hand in hand. Seeing that Exchange is very IO intensive, this is a very important point that can cause a lot of performance problems for Exchange clients.
 
Great read, please
go here to get it.

- Nino Bilic