Exchange 2003 Cluster

Exchange 2003 Cluster Consulting Services

Microsoft uses its own Exchange 2003 server clustering to provide communication within the company. At Microsoft, the Operations and Technology Group (OTG) manages the Exchange servers to keep them highly available and highly reliable.

OTG uses server clustering to ensure predictable and trustworthy messaging. A server cluster is a collection of servers that together provide a single, highly available system for hosting applications. To manage the high message traffic, OTG has implemented a clustering solution that makes Exchange servers at Microsoft available (in terms of global overall availability) more than 99.9% of the time (including both planned and unplanned outages).

In the server clusters that support messaging at Microsoft, each node runs Exchange 2003 and Windows Server 2003, Enterprise Edition. Windows Server 2003, Enterprise Edition supports up to eight nodes per cluster. Although OTG uses many server clusters in their operations, only one of the clusters used for internal messaging is described in this document. This unique cluster design has four active nodes, one primary passive node, and two alternate passive nodes. This design uses servers efficiently, and provides a reliable messaging environment that supports approximately 16,000 mailboxes.

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Reasons for Server Clustering

A server cluster is a collection of servers known as nodes that together provide a single, highly available system for hosting applications. Multiple nodes in a cluster remain in constant communication. A clusters resources and applications are organized into functional units called resource groups. Each resource group is assigned to a node and can only be owned by a single node at any point in time.

There are three primary benefits to using server clusters. Server clusters are highly available, scalable, and easy to manage.

Highly available: Server clusters provide a highly available system for deploying applications. You can use server clusters to protect against failures of hardware, operating systems, device drivers, or applications. If one of the nodes in a cluster is unavailable as a result of failure or maintenance, another node immediately begins providing service (a process known as failover). Server clusters also allow you to upgrade the operating system and application software with minimal downtime.
Scalable: Server clusters provide scalability for important resources and applications. When the overall load of a cluster exceeds its capabilities, you can incrementally add additional nodes to the cluster. In Windows Server 2003, server clusters can include up to eight nodes.
Easy to manage: In a server cluster, you can quickly inspect the status of all cluster resources and move workloads around onto different nodes. Because you can move processing to alternate nodes, you can perform rolling upgrades on the servers. In a rolling upgrade, a server cluster continues to provide service while software is being upgraded on each node until all nodes have been upgraded.

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Exchange 2003 Server Cluster Overview

The Exchange server cluster is based on an active/passive model, with a few alterations that maximize the performance of the hardware. The Operations and Technology Group (OTG) has configured a multinode cluster that consists of four active nodes, one primary passive node, and two alternate passive nodes. The four active nodes provide most of the processing operations for the messaging environment. Like most active/passive configurations, the primary passive node is used only when one of the active nodes fails or to support the process of rolling upgrades. The two alternate passive nodes are only used for messaging if failover occurs and the primary passive node is not available. To take full advantage of the available hardware, the alternate passive nodes are also used to facilitate the backup and upgrade processes. This unique configuration supports a total of 16,000 mailboxes.

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Diagram 1 Exchange Server Cluster

Diagram 1 shows the four active nodes, the primary passive node, and the two alternate passive nodes that make up the Exchange server cluster. All of the nodes are connected to two storage area networks (SANs). The two SANs provide communication between the nodes and the shared storage components, which are two redundant Enterprise Virtual Arrays. Each node in the cluster has two adapters that support a public network and a private network. The private network is reserved exclusively for internal communication between cluster nodes. The public network supports both node-to-node and client-to-cluster communication.

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