Operating System and Application Measures

Before you implement specific component-level and system-level fault tolerance measures, there are certain operating system and application measures to consider. Specifically, these measures include:

• Selecting Exchange and Windows editions

• Selecting client applications that support client-side caching

• Selecting and testing your server applications

• Using the latest software and firmware

Selecting Editions of Exchange and Windows

To provide the highest level of fault tolerance for your organization, make sure that you select the correct editions of Exchange and Windows. Although all editions of Exchange 2003 and Windows Server 2003 have been designed with high availability features, selecting the correct editions of each is an important step in maximizing the fault tolerance of your messaging system.

Selecting an edition of Exchange

You can select from two editions of Exchange 2003: Exchange Server 2003 Standard Edition and Exchange Server 2003 Enterprise Edition. The following table lists the key differences between these Exchange 2003 editions.

Key differences between Exchange 2003 Standard Edition and Exchange 2003 Enterprise Edition

For more information about the differences between Exchange 2003 Standard Edition and Exchange 2003 Enterprise Edition, see the Exchange Server 2003 Edition Comparison Web site.

For information that compares the features in Exchange Server 2003, Exchange 2000 Server, and Exchange Server 5.5, see the Exchange Server 2003 Features Comparison Web site.

Selecting an edition of Windows

You can select from three editions of Windows Server 2003: Windows Server 2003, Standard Edition; Windows Server 2003, Enterprise Edition; and Windows Server 2003, Datacenter Edition. If you want to use Windows Server 2003, Datacenter Edition, you must select a vendor that supports your Windows Server 2003 deployment scenario. For information about the Windows Datacenter High Availability Program, see the Windows Datacenter High Availability Program Web site.

For information about selecting an edition of Windows Server 2003, see the Introducing the Windows Server 2003 Operating Systems Web site.

For information about the high availability features of Windows Server 2003, see the Maximizing Availability on the Windows Server 2003 Platform Web site.

Selecting Client Applications that Support Client-Side Caching

When selecting a client application for your users, consider deploying Microsoft Office Outlook® 2003. Outlook 2003 supports client-side caching by using Cached Exchange Mode. When Outlook 2003 is used with Exchange 2003, you can configure Cached Exchange Mode to enable users to read e-mail messages or do other messaging tasks in low-bandwidth networks and in situations where network connectivity has been lost. Requests for information notifications from the Exchange server are eliminated on the user's Outlook client, allowing the user to work without interruption in low-bandwidth, high-latency networks. Moreover, Exchange 2003 and Outlook 2003 significantly improve client performance by reducing remote procedure calls (RPCs) and conversation between the Outlook client and the Exchange server. For more information about the performance advantages of using Outlook 2003 and Exchange 2003 together, see the Exchange Server 2003 Client Access Guide.

Selecting and Testing Server Applications

It is important that your server applications (for example, management scripts and antivirus software) are reliable. As a best practice, you should not run an application on a server until it has proven to be reliable in a test and pilot environment.

For information about laboratory testing and pilot deployments, see "Laboratory Testing and Pilot Deployments" in System-Level Fault Tolerant Measures.

For information about how to plan for unreliable applications, see "Operational Best Practices" in System-Level Fault Tolerant Measures.

Using the Latest Software and Firmware

Downtime for Windows and Exchange-based solutions can be the result of faulty device drivers, out-of-date software, or inadequate change control processes. To protect your Exchange 2003 organization against problems that hardware and software vendors have identified and corrected, keep your servers up-to-date with the latest software updates (such as hardware drivers) and firmware updates (such as basic input/output system [BIOS] updates). Most software application and hardware vendors have Web sites that provide software and firmware updates for their products.

Regarding your operating system updates, it is recommended that you regularly download the latest Windows Server 2003 software updates. Some Windows Server 2003 updates fix known problems or provide security enhancements. To download the latest Windows Server 2003 software updates, see the Microsoft Windows Update Web site.

However, before you deploy software and firmware updates in your production environment, make sure that you:

• Test the reliability of the updated software and firmware.

• Can back out of the updates if necessary.

Testing software and firmware updates in test environment

Before you install software and firmware updates on your production servers, you should deploy these updates in a test environment.

Backing out of software and firmware updates

You must also make sure that you can back out of any updates if problems occur. Depending on the type of update you install, there are different methods for backing out. For example, to back out of a driver update, you can use the Roll Back Driver feature in Windows Server 2003 Device Manager. For information about this feature, see the topic "To roll back to the previous version of a driver" in Windows Server 2003 Help.

In some cases, to back out of an update, you may have to restore the System State data, boot partition, and system partition backups from your server. For example, if you have a Windows backup set (which includes a backup of System State data, system partitions, and boot partitionsor a full computer backup set (which includes a backup of System State data and most of the data on your hard disks) prior to installing the updates, you can back out of some of these updates. You can also back out of some of these updates if you have images of your server's boot and system partitions prior to installing the updates.

For information about creating Windows backup sets and full computer backup sets, see the Exchange Server 2003 Disaster Recovery Operations Guide.

For information about how to keep these software and firmware updates readily available (for example, if you need to rebuild a server), see "Keeping Your Software and Firmware Updates Available" in the Exchange Server 2003 Disaster Recovery Planning Guide.