The second activity you must master to maintain your DCs proactively is performance management. When you use proper installation and creation procedures, your DCs should just work. Remember that the Domain Controller role is now in its fifth iteration since it  appeared in Microsoft Windows NT, and it has evolved with each release of the Microsoft server operating system. This means that it is now a very solid and stable service.
However, you’ll find that despite this stability, things can still go wrong, whether they are related to system or human errors. And when they do, you need to be ready to identify the issues quickly and take appropriate steps to correct the situation. When you perform proactive performance management, you are forewarned when untoward events might occur. This is the crux of this .

Some  important points are given below

– In Windows Server 2008 R2, you can use a series of tools to manage and monitor resource usage on a computer. These include Task Manager, event logs, Reliability Monitor, and Performance Monitor.
– Performance Monitor is now the single tool that regroups other tools used in previous versions of Windows. These tools included Performance Logs And Alerts, Server Performance Advisor, and System Monitor.
– You can use Windows System Resource Manager to control how resources behave on a scheduled basis. In fact, it provides two functions: It can monitor resource usage over time and log activity, and it can control access to resources based on specific policies.