Many applications and services are capable of taking advantage of clustering technologies to increase their availability. One of the most common cluster-aware applications in use today is Microsoft Exchange 2000.

Exchange is one of the most powerful enterprise messaging systems. Many businesses rely heavily on their messaging systems for their day-to-day operations and therefore require high availability. Exchange 5.5 was the earliest version of the application to provide support for clustering technologies. Exchange 2000 Enterprise Server provides support for Cluster Service allowing businesses to increase the availability of their messaging infrastructure.

Deploying Exchange 2000 in a cluster environment can eliminate some of the single points of failure, such as failed hardware or software components, associated with running a standalone system. As well, downtime resulting from planned outages for routing maintenance, upgrades, and configuration changes will be minimal.

Note: Exchange 2000 is available in different versions: Enterprise Server and Standard Server. To take advantage of the cluster technologies offered with Windows 2000 Advanced Server and Windows 2000 Datacenter Server, you must install Exchange 2000 Enterprise Server. Exchange 2000 Standard Server does not support clustering.

Exchange 2000 supports two cluster configurations: Active/Passive and Active/Active. In an Active/Passive configuration, Exchange runs on a single cluster node, while the other node remains idle. All the resources reside on the active node while the other one remains available should that active node fail. In an Active/Active configuration, each node in the cluster is running Exchange 2000, with at least one virtual server for each node. Because the service is running on each node, if a failure occurs, only the resources need to fail over to the second node, not the service itself.

Note: Each cluster node has the capability to support multiple virtual servers. For example, suppose Node A and Node B are both running Exchange 2000 and each are configured with an Exchange Virtual Server (EVS). If Node A fails, its EVS will fail over to Node B. Once the virtual server has failed over to Node B, clients can reconnect to it using its network name. The fact that the virtual server is now running on Node B is completely transparent to users.

Exchange is compromised of server different components. Some of these components are supported in a cluster environment and some are not. Of the components that can take advantage of clustering technology, some support and Active/Active configuration, where an instance of the component runs on each node. Other components only support an Active/Passive configuration, where there can only be a single instance running per cluster. The table below lists some of the Exchange components and the cluster configuration supported by each.

Note: Network News Transport Protocol (NNTP) is not supported in a cluster configuration but must be installed on each node that owns or could own an Exchange Virtual Server. If it is not already installed, it can be added through the Add/Remove Programs icon in the Control Panel.