With Windows 2000 Advanced Server and Datacenter Server, clustering is supported in the form of the Cluster Service. Exchange 2000 Enterprise Server also supports clustering, but Exchange 2000 Standard Server does not. A Cluster is basically a group of servers that appear as a single virtual server. A virtual server corresponds to a generic IP address and a network name, and allows users to access all the resources in the cluster, including Exchange 2000 services, without having to know the names of the individual nodes.

     Clustering is a mature technology and although is is not a 100% perfect solution, it does reduce the number of potential single points of failure. In the case of a system failure, the Cluster Service takes the virtual server offline on the first node before it takes it online again on another cluster member; hence, business processes are interruped, and users need to reconnect to the cluster after the failover. The advantage of clustering is that users can reconnect almost immediately. Clusters do not protect or repair information store databases, which remain single points of failure no matter how many nodes your cluster contains.

The Advantages of clustered Windows 2000 systems are:      With clustering hardware, a shared SCSI bus and two network cards are required in addition to typical server equipment, such as a local disk where the operating system must be installed. The shared SCSI bus allows all nodes access to the cluster disks. The Windows 2000 Cluster Service uses a "shared-nothing" model, also known as a paritioned data model, only one node at a time can access the shared SCSI drive. The node owning the resource requests exclusive access to the disk by using the SCSI Reserve command. No other node can then access the physical device unless an SCSI Release command is issued.

     Microsoft Outlook 2000 and Exchange 2000 are designed to overcome some of the shortcommings of the Clustering Service. When a cluster failover occurs, Outlook 2000 can reconnect to the cluster by simply switching to another folder in your mailbox (ie. inbox to contacts and then back to inbox)

Exchange 2000 Server Clustering Installation

     The installation of Exchange 2000 in a cluster is a process of four stages. First, you need to install Windows 2000 Advanced Server or Datacenter Server on all nodes and configure the cluster environment. In a second step, you have to install the Cluster services on the nodes and configure the cluster environment. Next, install Exchange 2000 Server on all nodes with exactly the same parameters. Next, configure and start virtual servers in Cluster Administrator.

     You cannot install Exchange 2000 on a nonclustered server and integrate this installation into a cluster afterwards. It is also a good idea to test the installation in a cluster prior to deploying Exchange 2000 in the production environment.

      When the Exchange 2000 Setup program detects the Cluster Service, it informs you that the cluster aware version of Exchange 2000 will be installed. It also sets the Exchange 2000 service to start manually. Do not start or stop Exchange 2000 services in the Services managmenet tool. You have to use Cluster Administrator to bring clustered services online or offline.

     When installing Exchange 2000 on each node (one at a time), it is important to use the same account you used to install the Cluster Service. It is also important to specify the same drive letters and directory on all the nodes in the cluster.

     Once Exchange 2000 Server is installed on all nodes, you are ready to configure resource groups. Each virtual server (or resource group) requires an IP address and a network name. Each Exchange 2000 server requires one or more shared disk resources where the Information Store databases must be placed. You cannot assign a single physical disk to more than one virtual server. All Exchange 2000 components depend on the SA, so you need to assign your virtual server and Exchange SA resource. Each resource group in a cluster must contain an IP address, network name, disk, and the Exchange SA resource. Other resources, such as automatically created protocol virtual servers, may be removed. Do not remove the Exchange Message Transfer Instance that you want to connect to Exchange 5.5 in a mixed-mode environment from the Exchange virtual server. The MTA is required for intrasite server to server communications.

     You can use the Exchange System Manager to configure additional virtual servers for Internet access protocols, however do not use the System Manager to bring a virtual server online in a cluster, use the Cluster Administrator by right clicking on the Exchange Cluster container, point to New, then select Resource to add a new resource that corresponds to the protocol of the virtual server you created with the Exchange System Manager. After you have created the resouce, you can right click the resource and choose Bring Online.

     Exchange 2000 supports full text indexing in active / active cluster configurations. The Exchange MS Search Instance resource is added to your virtual servers when you add the Exchange SA resource to your resource group. Even if you don't plan to use the full text indexing feature of Exchange 2000, do not delete the MS Search Instance from your virtual server. It is impossible to add it again without deleting and recreating the information store of the virtual server. As long as you do not create a full text index for a mailbox or public store with the Exchange System Manager, it will not affect the performance of your virtual server.

     To simulate a failover, open the Cluster Administrator and right click on an Exchange 2000 resource and select Initiate Failure. All resources in the cluster group will be taken offline and then brought back online on another available node in the cluster.