I have been rereading some sections of "Active Directory Bible" by Curt Simmons in preparation for some machine replacement and changes to our windows 2000 active directory infrastructure. It seems that in any relaible active directory network you should have at least two domain controllers so that logins and securities can be processed if one of them is down. However it is stated in this book that Logins require a GC. It is also stated that in a multi-domain controller network, the infrastructure role and the GC role should not be on the same machine, unless all of the domain controllers are GCs. He then says that you would never want to implement an active directory network with all machines as GCs. To quote the book - "However, unless you have a lot of excessive bandwidth you would like to eat up, you should certainly never implement such a solution."
So if you have a two domain controller network and the GC goes down, logon attempts will not work - in which case there is actually no redundancy. So would it really be that bad to have both DCs as GCs in a small (<35) machines network on a gigabit switch? It seems for all of the multiple domain controller redundancy that microsoft claims, there are a lot of single machine roles that can bring the whole thing crashing down in a machine failure. Am I wrong here?