I am installing Exchange 2007 to Server 2008 and have the OS on the C with Raid 1 and plenty of room, after the OS I was installed I still have over 50 gigs. I also have room on an external 4 disk Raid 10 array and have an app drive and a drive set aside for the Exchange DB. My initial feeling is to put it on the Raid 10 Array but am basically interested in finding which way might provide the best performance. Any suggestions? Its not got a whole lot of reduncancy but it is a fibre channel.