Samba domain controller setup for redundancy?
 

I am setting up 2 samba 3 servers to act as domain controllers for a network I am building.

What is the best way to ensure redundant domain controllers with always up to date SAM databases?

Or if I am asking the wrong question how do I ensure network login if either of my domain controllers go down. I am reading about a problem syncing SAM databases but I am not sure I understand the solution.

How about if use drdb filesystem for the shares and ha-cluster for the both servers connected to each other.