As discussed earlier in this online MCTS certification(http://www.mcts-70-620.com) lesson, when you install Active Directory on the first domain controller in a domain, a site object named Default-First-Site-Name is automatically created in the Sites container and the first domain controller for the domain is installed into this site. Subsequent domain controllers are installed either into the site of the source domain controller (assuming the IP address maps to the site) or into an existing site. Domain controllers might also need to be demoted. Therefore, it is often necessary to create, move, or remove domain controller objects in a site. However, you must first consider the location of domain controllers for each site.
Determining the Location of Domain Controllers
For optimum network response time and application availability, place at least
One domain controller in each site A domain controller in each site provides users with a local computer that can service query requests for their domain over LAN connections.
Two domain controllers in each domain By placing at least two domain controllers in each domain, you provide redundancy and reduce the load on the existing domain controller in the domain. Recall that a domain controller can service MCTS benefits(http://www.mcts-70-620.com) only one domain.
When a single site includes multiple domains, you cannot place a domain controller in the site and expect it to service more than one domain.
Reasons for placing additional domain controllers in a site are the following:
There are a large number of users in the site, and the link to the site is slow or near capacity. If a site has slow logon times and slow authentication when attempting to access user resources, capacity might be insufficient. By monitoring domain controller usage, you can determine whether there is enough processing power and bandwidth to service requests. If performance is lagging, you should
consider adding another domain controller to the site.
The link to the site is historically unreliable or only intermittently unavailable.If a single domain controller in a site fails, clients can connect to
other domain controllers in other sites in the domain by crossing site links. However, if site links are unreliable, users on that site may not be able to log on to their computers. In this case, you should consider adding another domain free Microsoft certification exam papers(http://www.examshots.com/vendor/Microsoft-1.html) controller to the site.


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