i’m having the same problem (in server 2003).
I recently added another DC and added the DNS role and configured it as a primary AD integrated server.
the “backup” DC (BDC) has itself set as its preferred DNS server and the PDC as its secondary.
However, if i shut down the PDC – i lose all DNS on the network.
I’m havent checked if i lose ability for users to authenticate, but I know that DNS doesnt “Fail over” to the BDC.
Which kinda defeats the purpose of having added the BDC (lol hooray for virtualisation)
p.s – i dont even know what fsmo roles are…….. or why i would transfer them?