Considering Cost Restraints

Business requirements, particularly cost constraints, determine whether it is cost-effective to upgrade the network infrastructure, server hardware, and software in your messaging environment. To maximize the financial resources of your hardware and software budget, you must first analyze the integrity, performance, and features within your existing messaging environment. Then, you must decide which upgrades are necessary to meet business and user requirements.

As you determine how much to invest in your high availability strategy, consider the following:

• Understand the value of high availability in each aspect of your business   For example, in a high-traffic commerce Web site, each hour that a Web server's databases are unavailable may cost up to $100,000 in sales. However, for that same company, the cost impact of an unavailable messaging system may be much less. In this example, you should maintain a higher availability level for your Web servers (for example, 99.99 percent), and a lower availability level for your mailbox servers (for example, 99.9 percent).

• Research the actual costs of downtime of your messaging services   In general, the costs associated with messaging service downtime are usually much higher than you would initially expect. Researching these costs helps you determine if the costs of implementing and maintaining a high availability solution are less than the costs of downtime. For more information about the cost and impact of downtime, see "Costs of Downtime" and "Impact of Downtime" in Understanding Downtime.

• Understand how your hardware and software directly impacts availability   Your hardware and software choices directly affect the performance, design, and availability of your Exchange messaging system.

• Understand that costs of downtime are non-linear   For example, the consequences of a five-minute outage may far outweigh those of five one-minute outages.

If cost constraints prevent you from purchasing expensive hardware, you can maximize your available resources to achieve a high level of performance and availability. For example, to minimize the amount of time it takes to restore data, you can implement a backup strategy that requires more frequent backups. Costs related to this backup strategy are much less than those associated with backup strategies that include a Storage Area Network (SAN)-based Volume Shadow Copy service. For information about how you can minimize the amount of time it takes to recover Exchange data, see "Implementing Practices to Minimize Exchange Database Restore Times" in the Exchange Server 2003 Disaster Recovery Planning Guide.

Similarly, in cases where networking upgrade possibilities are limited, you can take advantage of messaging features such as RPC over HTTP and Exchange Cached Mode. These features help provide a better messaging experience for your users who have low-speed, unreliable network connections. For more information about the fault tolerant features in Exchange 2003, Microsoft Windows Server™ 2003, and Microsoft Office Outlook® 2003, see Operating System and Application Measures.