I got the which computers can be export computers. Which ones can import files. I got the backing up the registry file one. For security you assign roaming mandatory profiles for all user accounts. The server that has the profiles fails .
Users can still logon using a profile from one of the other domain controllers.
Users can choose to logon to one of the other domain controllers and use the default profile. Users will not be able to logon. Users will log on successfully and will receive the default user profile. You have 3 Win NT servers with RAS installed on 3 different network segments. Win NT workstations dial in.