Examining Exchange Server 2003 Performance Improvements

Before delving into ways to tweak Exchange Server 2003 performance, it is important to have an understanding of the performance improvements that have been made since its predecessor, Exchange 2000. Although some of these performance improvements are more noticeable than others, Exchange Server 2003 has proven its ability to scale into the enterprise and beyond.

Communication Improvements

Exchange Server 2003 includes major improvements in the way it handles client/server communications. These improvements entail changes made to communication links between sites, servers, and users. Implemented changes translate into a fundamentally different approach toward how Exchange Server 2003 handles routing of messages from site to site as well as to and from the client computer.

Improvements in Link State Connections

In order to determine the best possible route to send a message between servers, Exchange uses link state routing technology. The best route is chosen based on the status and the cost of the connections. While routing messages between servers and sites, no alternate paths might be available to Exchange Server 2003 servers, or the existing connectors might be intermittently available. By determining whether there are alternate and available connections, Exchange Server 2003 significantly reduces the amount of traffic between servers.

Another performance improvement with Exchange Server 2003 analyzing links between servers is how it efficiently propagates link status information to other servers in and between sites. If no alternate paths are detected for a message to take, the available route is marked as always in service. Exchange will never change this state back to an out-of-service state unless an alternate path becomes available. As a result, propagation of link state information in and between sites is reduced, and consequently overall network traffic is optimized.

Synchronization and Replication Enhancements

Synchronization and replication enhancements available in Exchange Server 2003 can be analyzed from various viewpoints. Generally speaking, these enhancements include changes made to the Outlook client, Outlook Web Access client, and public folders.

Client-side Performance Enhancements

Among the new performance-enhancing features of Exchange Server 2003 and Outlook 2003 is the ability to collect client-side data by recording RPC errors that occur on the client. This information is then reported in the Event Viewer.

Outlook 2003 Client Synchronization

Significant reduction of Remote Procedure Calls (RPCs) to the Exchange Server from the Outlook 2003 client has resulted in noticeable improvements in client performance even in low-bandwidth conditions. This improvement was primarily made available through the employment of the following features:

• Cached Exchange Mode Cached Exchange Mode refers to the Outlook 2003 client keeping a local copy of the user's mailbox on the client computer. This is similar to an Offline Folder (OST) file in earlier versions of Exchange. There are some differences, however: This mode requires less configuration (as shown in Figure 33.1), uses the Offline Address Book (OAB) by default, and copies the entire mailbox rather than relying on the user to specify which folders to synchronize with Exchange Server 2003. Although this reduces the number of data requests sent to the server, this mode also determines whether or not the connection with Exchange is slow (128KB or less) and then adapts accordingly . For instance, if the user connects via the corporate LAN, the full message, including attachments, is copied to the local cached copy. If the user later connects using a 56KB modem, only headers are copied unless the user opens the message. This is done automatically and is transparent to the user.

  Figure 33.1. Cached Exchange Mode option.

  

• Outlook Synchronization Synchronization communication between the Outlook client and Exchange Server 2003 uses data compression to reduce traffic overhead. Changes that are made through the Outlook client are also sent to Exchange Server 2003 incrementally, thereby providing additional network traffic optimization.

Outlook Web Access (OWA) Performance Enhancements

An abundance of new features are available in OWA, and the biggest one by far is the interface. However, the following primary features contribute to performance enhancements:

• Compression Support OWA compression uses GZip to keep bandwidth requirements low and improves response times even over dial-up or other low-bandwidth connections. Configuring OWA to use high compression (that is, compression of static and dynamic pages) can reduce bandwidth requirements as much as 50%. It is important to note that clients must use Internet Explorer (IE) 6 (or Netscape 6) or higher in order to take advantage of OWA compression.

• Logon Options Outlook Web Access is now available in two configurations: Premium and Basic Experience. These two configurations are presented to users at the time of login and depending on available bandwidth, the user can choose which version of OWA to load, thus improving performance.

Improved Public Folder Store Replication

Public folder store replication has greatly improved in respect to the way Exchange Server 2003 handles the receipt of updates from various other servers. In Exchange 2000 Server, a server holding the largest number of needed updates would always be chosen regardless of its transport cost. When determining update status during the replication process, Exchange Server 2003 takes the following three main elements into account on a priority basis and calculates the replication algorithm based on the data gathered from these questions:

• Which server has the lowest transport cost?

• For servers with equal transport costs, which server is the newest version of Exchange?

• For servers with equal transport costs and versions, which server owns the greater number of updates?

This architecture enables reduction of replication traffic over slower links because lower-cost servers (servers in the same site) always take precedence over higher-cost servers (those located in remote sites).

Performance Scalability Improvements

Some of the Exchange Server 2003 enhancements to performance and scalability are

• Improved Distribution List Member Caching The processing resources required to look up the membership of Distribution Lists has been greatly reduced by redesigning the cache rule in a way that lookups and insertions can be achieved by 60% fewer Distribution List “ related queries made against Active Directory. Therefore a small AD performance optimization has been achieved by changes made to the cache rule.

• Enhanced Internet Mail Delivery Exchange Server 2003 relies heavily on Windows Server 2003 DNS for message delivery, and the algorithms used relating to load-balanced DNS-based Internet delivery have been enhanced. In circumstances where the external DNS Server is not available or the network is experiencing latency, Exchange Server 2003 has greater tolerance, which results in a greater reliability of message delivery.