6.3. Adding a Second DC

Whenever possible, you should have a second DC. A second DC will make routine maintenance and disaster recovery planning much simpler. A single domain controller is a significant single point of failure risk. If it goes down, your entire network can go down, and you'll find yourself in crisis mode.

If you have a second DC and either the first or second DC fails, the network will continue to hum along. Users will still be able to log onto the domain, and they won't experience any interruption in their work, group policies will still be applied, and normal administration of the domain can still be done. You'll still have work to do, but it won't be a crisis. Additionally, restoring a failed DC is much simpler if a DC is still running in the domain. You can even create a new DC from scratch without a backup if it comes to that.