Setting Availability Goals
When designing your Microsoft® Exchange Server 2003 messaging system, consider the level of availability that you want to achieve for your messaging service. One important aspect of specifying an availability percentage is deciding how you want to measure downtime. For example, one organization may consider downtime to occur when one database is not mounted. Another organization may consider downtime to occur only when more than half of its users are affected by an outage.
In addition to availability levels, you must also consider performance and scalability. By ensuring that your messaging system resources are sufficient to meet current and future demands, your messaging services will be more available to your users.
Availability goals allow you to accomplish the following tasks:
Keep efforts focused where they are needed. Without clear goals, efforts can become uncoordinated, or resources can become so sparse that none of your organization's most important needs are met.
Limit costs. You can direct expenditures toward the areas where they make the most difference.
Recognize when tradeoffs must be made, and make them in appropriate ways.
Clarify areas where one set of goals might conflict with another, and avoid making plans that require a system to handle two conflicting goals simultaneously.
Provide a way for administrators and support staff to prioritize unexpected problems when they arise by referring to the availability goals for that component or service.
This section, together with the information provided in Understanding Availability, will help you set availability goals for your Exchange Server 2003 organization. Well-structured goals can increase system availability while reducing your support costs and failure recovery times.
To help set your availability and scalability goals, read this section in conjunction with Questions to Consider When Developing Availability and Scalability Goals.