Express existing usage patterns as clearly measurable goals for the deployment to achieve. Here are some questions that will help you determine such goals.
How are current services utilized?
Can your users be categorized (for example, as sporadic, frequent, or heavy users)?
How do users access services (from their desktop, from a shared PC or factory floor, from a roaming laptop)?
What size messages do users commonly send?
How many invitees are usually on calendar appointments?
How many messages do users send?
How many calendar events and tasks do users typically create per day or per hour?
To which sites in your company do your users send messages?
What level of concurrency, the number of users who can be connected at any given time, is necessary?
Study the users who will access your services. Factors such as when they will use existing services are keys to identifying your deployment requirements and therefore goals. If your organization’s experience cannot provide these patterns, study the experience of other organizations to estimate your own.
Regions in organizations that have heavy usage might need their own servers. Generally, if your users are far away from the actual servers (with slow links), they will experience slower response times. Consider whether the response times will be acceptable.