We have 2 Domain Controllers running Windows Server 2003 R2 x64. DC1 has the FSMO roles and DC2 acts as a 'secondary' DC. Both are Global Catalog servers.
DC1 has these roles installed: Domain Controller, DNS Server, Application Server (IIS), File Server and Print Server. DC2 has these roles installed: Domain Controller, DNS Server, Application Server (IIS) and File Server.
There is also a trust relationship between the current domain of these two DCs and a different one which is located in the same location.
What we want to achieve is to upgrade both servers to Windows Server 2008 R2 with a clean install process on both machines, not a direct upgrade from 2003 R2 to 2008 R2.
I am looking for the best practice to achieve that goal. Can you please help me understand the best way to achieve that?
Which server do I have to upgrade first? How can I preserve all of the settings and data from each role?