In reading all the design and planning information I have found very little as to AD performance for 2007. There is a vague reference to a 4:1 ratio of Exchange processors to GC processor. Does this apply if your 64 bit exchange to 32 bit AD? Currently I'm at the 4:1 for 2003 with no noticable affect to GC performance, but when I have 2007 installed should I also have 64 bit AD. We are targeting a 3k to 4k exchange user environment when we further consolidate to 2007 and if we have to take AD to 64 bit we won't be doing a 2007 transition any time soon. Anyone have some good links to actually AD 32/64 performance numbers with 2007? Thanx

I don't think there are many changes in LDAP operations when going from Exchange 2003 to Exchange 2007 You don't need a 64 bit AD, this has nothing to do with Exchange being 64 bit Exchange 2007 works fine with 32 bit AD domain controllers You might consider using 64 bit domain controllers if you want to increase your performance of your domain controller only if you have a very large AD database. (you can view your NTDS.DIT file for the size) But going forward with your 4k users I don't think that your DB will be very large, it is probably arround 300 to 400 MB This will fit easily in the memory of a 32 bit domain controller Read this article on AD performance 32bit vs 64bit http://www.microsoft.com/downloads/details.aspx?FamilyID=52e7c3bd-570a-475c-96e0-316dc821e3e7&displaylang=en (If your AD DB would be larger than 2GB then you will benefit very much for using 64 bit domain controllers as they can load the entire DB into memory as opposed to 32 bit Domain controllers) But for you it is sufficient to have 32 bit domain controllers Deli