You can add domain controllers to a domain to improve load balancing within a site and fault tolerance for the domain. Additional ...

You can add domain controllers to a domain to improve load balancing within a site and fault tolerance for the domain. Additional domain controllers improve performance of authentication requests and global catalog server lookups. They also help Active Directory Domain Services (AD DS) overcome hardware, software, or administrator errors. To add a domain controller, information is replicated over the network or by using backup media from another domain controller in the domain.