Sun Java System Calendar Server 6 2004Q2 Deployment Planning Guide |
Chapter 2
Analyzing Your RequirementsPlanning your Calendar Server deployment requires that you first analyze your organization’s business and technical requirements. This chapter helps you to gather and assess your requirements, which you then use to determine your Calendar Server architecture.
This chapter contains the following sections:
Identifying Deployment GoalsBefore you purchase or deploy Calendar Server software or hardware, you need to identify your deployment goals. Deployment requirements can come from various sources within an organization. In many cases, requirements are expressed in vague terms, requiring you to clarify them towards determining a specific goal.
The outcome of your requirements analysis should be a clear, succinct, and measurable set of goals by which to gauge the deployment’s success. Proceeding without clear goals accepted by the stake holders of the project is precarious at best.
Some of the requirements you need to examine before you can plan your deployment include:
Business Requirements
Your business objectives affect deployment decisions. Specifically, you need to understand your users’ behavior, your site distribution, and the potential political issues that could affect your deployment. If you do not understand these business requirements, you can easily make wrong assumptions that affect the accuracy of your deployment design.
Operational Requirements
Express operational requirements as a set of functional requirements with straightforward goals. Typically, you might come across informal specifications for:
For example, translate a requirement for “adequate end-user response time” into measurable terms such that all stake holders understand what is “adequate” and how the response time is measured.
Culture and Politics
A deployment needs to take into account your corporate culture and politics. Demands can arise from areas that end up representing a business requirement. For example:
Technical Requirements
Technical requirements (or functional requirements) are the details of your organization’s system needs.
Supporting Existing Usage Patterns
Express existing usage patterns as clearly measurable goals for the deployment to achieve. The following questions will help you determine such goals.
- How are current services utilized?
- Can your users be categorized (for example, as sporadic, frequent, or heavy users)?
- What size messages do users commonly send?
- How many invites 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?
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, they will experience slower response times. Consider whether the response times will be acceptable.
Site Distribution
Use these questions to understand how site distribution impacts your deployment goals:
Network
The following questions help you understand your network requirements:
- Do you want to obfuscate internal network information?
- Do you want to provide redundancy of network services?
- Do you want to limit available data on access layer hosts?
- Do you want to simplify end-user settings, for example, have end users enter a single mail host that does not have to change?
- Do you want to reduce network HTTP traffic?
Existing Infrastructure
You might be able to centralize servers if you have more reliable and higher available bandwidth.
Support Personnel
24-hour, seven-day-a-week (24 x 7) support might only be available at certain sites. A simpler architecture with fewer servers will be easier to support.
Financial Requirements
Financial restrictions impact how you construct your deployment. Financial requirements tend to be clearly defined from an overall perspective providing a limit or target of the deployment.
Beyond the obvious hardware, software, and maintenance costs, a number of other costs can impact the overall project cost, including:
You can avoid financial issues associated with the project by applying sufficient attention and analysis to the many factors associated with the project requirements.
Service Level Agreements (SLAs)
You should develop SLAs for your deployment around such areas as uptime, response time, message delivery time, and disaster recovery. An SLA itself should account for such items as an overview of the system, the roles and responsibilities of support organizations, response times, how to measure service levels, change requests, and so forth.
Identifying your organization’s expectations around system availability is key in determining the scope of your SLAs. System availability is often expressed as a percentage of the system uptime. A basic equation to calculate system availability is:
Availability = uptime / (uptime + downtime) * 100
For instance, a service level agreement uptime of four nines (99.99 percent) means that in a month the system can be unavailable for about four minutes.
Furthermore, system downtime is the total time the system is not available for use. This total includes not only unplanned downtime, such as hardware failures and network outages, but also planned downtime, preventive maintenance, software upgrade, patches, and so on. If the system is supposed to be available 7x24 (seven days a week, 24 hours a day), the architecture needs to include redundancy to avoid planned and unplanned downtime to ensure high availability.
Determining Project GoalsYour investigation and analysis should reveal your project’s requirements. Next, you should be able to determine a clearly measurable set of goals. Specify these goals in such a manner that personnel not directly associated with the project can understand the goals and how to measure the project against them.
Stake holders need to accept the project goals. The projects goals need to be measured in a post-implementation review to determine the success of the project.
Planning for GrowthIn addition to determining what capacity you need today, assess what capacity you need in the future, within a timeframe that you can plan for. Typically, a growth timeline is in the range of six to twelve months. Growth expectations and changes in usage characteristics are factors that you need to take into account to accommodate growth.
As the number of users and messages increase, you should outline successful guidelines for capacity planning. You need to plan for increases in message traffic for the various servers, a larger volume of users, larger mailbox sizes, and so forth. As growth occurs in the user population, usage characteristics change over time. Your deployment goals (and therefore deployment design) must respond accordingly to be viable into the future.
Ideally, you should design your architecture to easily accommodate future growth. Monitoring the deployment, once it enters its production phase, is also crucial to being able to understand when and by how much a deployment needs to grow.
Understanding Total Cost of Ownership
Total Cost of Ownership (TCO) is another factor that affects capacity planning. This includes choosing the hardware upon which to deploy your Calendar Server. Table 2-1 presents some factors to consider as to whether to deploy more smaller hardware systems or fewer larger hardware systems.