To recover a domain controller through reinstallation, you do not restore the system state from backup media; instead, you reinstall Windows, install Active Directory, and allow replication partners to bring the recovered domain controller up to date. Recovering a domain controller through reinstallation can quickly return the computer to service if the following conditions exist: First, a domain controller has failed and you cannot restart in Directory Services Restore mode. If failure was caused by a hardware failure, you have resolved the hardware problem (for example, by replacing the disk). Second, there are other domain controllers in the domain, to serve as replication partners. Third, the computer is functioning only as a domain controller (it does not run other server services such as Exchange), and it does not contain other data that needs to be recovered from a backup. (technet.microsoft.com)
Monitoring is an essential part of server administration. By monitoring the server 's performance, you can spot problematic trends as they develop, and take steps to prevent them from
Cited: TechNet – Microsoft “Active Directory Backup and Restore”, 14 February 2014 Manage – Engine “Windows Active Directory Monitoring”, 10- January 2013