Backup Domain Controller?

[Tom Del Rosso]

What I've read of Active Directory says that MS did away with the model
of Primary and Backup DC. Isn't there a system of making the Active
Directory server redundant?

 

[me]

if you have multiple domain controllers, active directory replicates itself
to the other dc's automatically

 

[Richard G. Harper]

All domain controllers in an Active Directory domain are equal partners as
far as the domain security and configuration are concerned. Active
Directory replicates the domain information between all domain controllers
that are present.