There seems to be a great deal of confusion currently around the question of migrating to Exchange 2010 - Everyone seems pretty intent on doing it, but many find it hard to identify the correct upgrade path to suit thier current environment. Exchange has always had a specific combination of operating systems on which it could be installed. Now with the release of Exchange 2010,Windows Server 2008 R2 and Exchange 2007 Service Pack 2, that has not become any easier!
First, what migration paths did we have in the past? Exchange 2000 was in-place upgradable to Exchange 2003. If Exchange 2000 was installed on Windows 2000, you then could in-place upgrade to Windows 2003 with taking al those benefits that come with that (never recommended by myself!). An in-place upgrade from Exchange 2003 to Exchange 2007 wasn’t possible, mostly due to the required x64 architecture requirements. Migrating to Exchange 2007 is directly supported from Exchange 2000 and 2003 (mailbox swing).
What about migrating to Exchange 2010 then? Active Directory must be at Windows Server 2003 forest functionality mode or higher. Another important requirement for migration to Exchange 2010 is that you at least have Exchange 2003 SP2 or Exchange 2007 SP2 installed in the environment! So no co-existence with Exchange 2000. What kind of consequences will that have on your migration path? I know that a large number of businesses still run Exchange 2003 (its a GREAT product) and even now some still use Exchange 2000 on Server 2000, which makes it a very valid question.
Well, simply put: you will have to migrate from Exchange 2007 with Service Pack 2 on either Windows 2003 x64, 2008R2 or 2008 x64 or you have to in-place upgrade or transition your Exchange 2000 installation to Exchange 2003 SP2. Alternatively, you can transition directly from Exchange 2000 to Exchange Server 2007 SP2 and then transition to Exchange 2010. Note that an in-place upgrade of Exchange 2007 to Exchange 2010 isn't supported.
Reading the above is still confusing, so I’ve made an illustration depicting the migration paths below that works better!!
So, There are no real problems migrating to Exchange Server 2010, they are comparable to the paths you had to take with Exchange 2007. Extra steps have to be taken if you are still using Exchange 2000, but the vast majority of my customers (>90%) are sitting in Exchange 2003 or Exchange 2007. Those who already migrated to Exchange 2007, install Service Pack 2 which is readily available.
I hope this clears up at least some of the confusion 🙂 Feedback, as always is welcome