|I'm not sure I understand your question about the RAID. Since RAID is primarily used to protect against hardware failure or to increase throughput/capacity limited by the hardware, you would just set it up as you have before. It doesn't matter what you are running on the computer.|
As to the DMZ idea, I don't quite get why you provided this information. I assume you are using DMZ to mean a completely un-firewalled/un-NATed computer. If that is the case, I would suggest you instead just forward the appropriate ports to the appropriate interfaces. There is no need to have Exchange server or anything else completely open, when the Exchange services you need access to only use a few specific ports.
As to where to install Exchange, that is pretty much up to you. Exchange doesn't really care if it is on a virtual computer or a real computer, provided it has the resources necessary for it's particular application.
PS: Nice website, but be sure to spell/grammar check your writing.
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