I'm currently researching the upgrade process to Unity 5.0(1), and I would like some advice on a few configuration issues. I have 2 clusters with Unity 4.0(5) VMO, both with failover and they are digitally networked together. One cluster is running server 2000. The other cluster is running server 2003. I also have off box exchange. The upgrade path I'm thinking of doing is to do a rolling upgrade on the cluster that has 2003 on it, and then on the cluster that is 2000. Take a dirt backup, reload with 2003 install Unity 4.0(5) back on it and then do a dirt restore. Once the dirt is complete then do the rolling upgrade to Unity 5 on this cluster. I have a question though about this, can you have a Unity 4.0(5) and a Unity 5 cluster digitally networked together? Any help or advice is greatly appreciated.