Branch Office-to-Hub Replication Overload (Inbound Overload)

Updated: June 3, 2009

Applies To: Windows Server 2008

Inbound overload occurs when a bridgehead server is trying to replicate (pull) changes from more domain controllers than it can handle. As a bridgehead server attempts replication, the replication queue begins to grow because the server does not have time or the hardware resources to service all the requests before a new cycle begins. As this situation progresses, more requests are added to the queue that are higher priority and they are placed in the queue ahead of the lower-priority items. An overload condition exists if there are items in the queue that are never serviced because higher-priority items are always placed in front of them.

If you have read-only domain controllers (RODCs) in branch offices, there will be no inbound overload on bridgehead servers because there is no replication from RODCs to the hub servers. For the most part, you have to monitor inbound overload on bridgehead servers only while you still have writeable domain controllers in the branches.

You can best resolve the problem of inbound overload by replacing the Windows Server 2003 domain controllers in branch offices with Windows Server 2008 RODCs, adding another bridgehead server in the hub site, or extending the replication schedule.

Two tools that you can use to detect inbound overload are Repadmin and Adlb.exe. You can run the repadmin command with the /queue option to check the size of the queue. You should run this command while the replication schedule is closed so that you can check to see if the queue is empty. If the result never reaches zero, the bridgehead server is overloaded. You can use Adlb.exe to generate a loading report.

If your environment has not been load-balanced, Adlb.exe might be able to redistribute connections to reduce the load on some writeable domain controllers. Adlb.exe works only with writeable domain controllers.

If you use Adlb.exe, be sure to use the version of this tool that is included with the download package for the Windows Server 2003 Active Directory Branch Office Guide (http://go.microsoft.com/fwlink/?LinkID=28523).

For File Replication Service (FRS) and Distributed File System (DFS) Replication, monitor the inbound connections. For more information, see Monitoring Your Branch Office Environment.

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