Microsoft KB Archive/815180

= Considerations when deploying Exchange on an Active/Active cluster =

Article ID: 815180

Article Last Modified on 10/25/2007

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APPLIES TO


 * Microsoft Exchange Server 2003 Enterprise Edition
 * Microsoft Exchange Server 2003 Standard Edition
 * Microsoft Exchange 2000 Server Standard Edition

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SUMMARY
This article discusses some of the things to consider when you deploy Microsoft Exchange 2000 Server or Microsoft Exchange Server 2003 in an Active/Active clustered environment.



MORE INFORMATION
Microsoft does not recommend the deployment of Exchange 2000 servers or Exchange 2003 servers in an Active/Active clustered environment. Additionally, Exchange 2000 and Exchange 2003 are supported as Active/Active in two-node clusters only. Clusters that have more than two nodes must be Active/Passive. For more information about this subject, click the following article number to view the article in the Microsoft Knowledge Base:

329208 Exchange virtual server limitations on Exchange 2000 clusters and Exchange 2003 clusters that have more than two nodes

In an Active/Active cluster, when one node fails or is taken offline, the other node in the cluster takes over for the failed node. However, because the failover causes the remaining node to take on additional processing operations, the overall performance of your Exchange 2000 cluster or Exchange 2003 cluster may be reduced. For performance, availability, and scalability reasons, Active/Passive cluster configurations are a better option than Active/Active configurations.

In a typical Active/Active cluster configuration, each node owns one Exchange virtual server. However, if the number of Exchange virtual servers in the cluster is greater than or equal to the number of nodes in the cluster, and even when all the Exchange virtual servers are owned by only one node in the cluster, the cluster is still considered an Active/Active cluster. To migrate from an Active/Active cluster configuration to an Active/Passive configuration, you must remove the second Exchange virtual server. For information about how to remove an Exchange virtual server, see the &quot;Removing an Exchange virtual server from a Cluster&quot; section in the Deploying Microsoft Exchange 2000 Server Clusters Exchange Online Book. To view this Exchange Online Book, visit the following Microsoft Web site:

http://go.microsoft.com/fwlink/?LinkId=9393

Sizing Active/Active clusters
When you plan your Exchange 2000 topology using Active/Active clusters, you must consider the following important constraints:  Make sure that the number of concurrent user connections per cluster node is not greater than 1,900. If you have more than one Exchange virtual server per cluster node, make sure that the sum of all concurrent user connections for each of the two nodes is fewer than 1,900. Each user may make more than one connection. Therefore, the number of mailboxes may not be an accurate way to estimate the number of connections. If one node of the cluster is unavailable and if all Exchange virtual servers (EVSs) are online on a single node, the scaling limits remain at 3,800 connections for the two EVSs. Scaling limits exist to make sure that failover into a node that is already running an instance of Exchange is successful. This constraint does not apply when there is no other node available for failover. Make sure the average CPU load per server is not greater than 40 percent. Exchange 2000 installed on an Active/Active cluster has the same limitations as a stand-alone computer that is running Exchange 2000. These limitations are:  A maximum of four storage groups. A maximum of five databases per storage group. A maximum of one public folder store per public folder hierarchy.

For more information, click the following article number to view the article in the Microsoft Knowledge Base:

222989 Relationship between storage groups, databases, and transaction logs

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After you deploy your Active/Active Exchange Server cluster, you must monitor the following items:
 * The number of concurrent connections (users) per node. If the number of concurrent users per node is greater than 1,900 for more than 10 minutes, move users off the node until the number of concurrent connections is less than 1900.
 * The CPU load for each server in the cluster. If the CPU load is greater than 40 percent (load generated from users) for more than 10 minutes, move users off the server until the CPU usage is reduced to 40 percent or less. This load does not include CPU usage related to administrative tasks such as moving users, or other server management tasks.

For additional information about deploying Exchange 2000, see the Deploying Microsoft Exchange 2000 Server Clusters Exchange Online Book. To view this Exchange Online Book, visit the following Microsoft Web site:

http://go.microsoft.com/fwlink/?LinkId=9393

For additional information about deploying Exchange 2003, see the Exchange 2003 Deployment Guide. To view the Exchange 2003 Deployment Guide, visit the following Microsoft Web site:

http://technet.microsoft.com/en-us/library/bb123872.aspx

For more information about how to implement Exchange 2000 Server on a Windows 2000 cluster, click the following article numbers to view the articles in the Microsoft Knowledge Base:

328875 How to implement Exchange 2000 Server on a Windows 2000-based cluster

810986 Microsoft support policy for Exchange Server installed on cluster nodes

Additional query words: XADM MSCS

Keywords: kbinfo KB815180

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