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This chapter is from the book

This chapter is from the book

Maintaining Capacity Plans

Capacity plans are living documents. They need to be actively managed as your organization and its needs change. This section describes the procedures you can use to make sure your capacity plan is always ready to support the decisions that need to be made. By thinking about maintenance before plans are made, you will never be in a position to have to refresh dozens or even hundreds of out-of-date plans at the same time.

Periodic Reviews

The first issue to consider is how to keep capacity plans current as your organization's IT needs and projects change. Every organization goes through normal cycles when they need more capacity or less capacity. Therefore, every capacity plan is incorrect at least some of the time. You should conduct periodic reviews of each of your plans to bring them back in line with the actual issues, utilization, and capacity of your IT infrastructure.

Most organizations find a quarterly cycle to be best for capacity plan reviews. This allows enough time to go by for changes to happen, but doesn't let the plans get so far out of date that they are not effective when needed. Three months should be adequate time for most organizations to consider the recommendations made by the capacity plans and to implement those that are most critical. If your organization is particularly small or has very infrequent changes, you might consider a longer cycle, but certainly no more than every six months. Conversely, for very large or very dynamic organizations you might want to look at capacity plans more frequently. One very large client I worked with broke the capacity plans into areas by technology and had a monthly meeting for each area to review all the capacity plans that impacted that area. I cannot imagine needing a review any more than monthly.

After you've defined the review cycle, you need to establish a mechanism that reminds you when reviews are needed. With dozens or even hundreds of separate plans, you need to create a capacity plan review schedule that indicates which plans are up for review at what time. The best way to do this is with a document management system with built-in review policies. If you don't have a good system, you will most likely need to create an inventory of each of the capacity plans tracking their owner (more about that later), their last review date, and their next scheduled review date. Then as a capacity manager you are responsible for reviewing that inventory and setting up the appropriate reviews. Regular reviews must be a high priority because the expense of starting over again with capacity plans can be steep.

What should you look for as you're doing a review? You should review the pieces that change most frequently, which include the utilization and the analysis sections. The utilization either confirms or contradicts the analysis you have done in the past. If your predictions of the future were reasonably accurate, your analysis should still be sound. On the other hand, if you find that actual utilization has differed dramatically from what you predicted, you may want to read Chapter 3 again and find a more accurate way to predict demand. The entire validity of the capacity plan is based on the accuracy of your utilization predictions, so you should take every opportunity to learn to predict capacity demand more accurately.

The analysis and recommendations will likely change with every review of the capacity plans. If the recommendations were implemented, you will have new capacity and those recommendations can now be removed from the plan. For recommendations that were not adopted, however, you will want to review whether the recommendation is still valid, and if so, strengthen it to show why it should be adopted soon.

Capacity plan reviews should take place in a joint meeting between the technicians responsible for managing the capacity pool, the capacity manager, and someone with financial authority responsibility for the capacity pool. The technician is generally able to document how accurate the utilization predictions were, the capacity manager can describe any activities that have changed the total capacity or impacted the recommendations in the plan, and the financial manager can indicate which new recommendations are likely to get funded. This meeting does not need to take a long time or be extremely formal—the participants just need to touch base to agree together on the changes to be made to the plan.

In lieu of an actual meeting, it is possible for the capacity manager to update the plan with recommended changes and have the other two approve those changes through email. This removes some of the interplay that is likely in a meeting, but reduces the time commitment that each person must make. In many cases these "off line" reviews are needed because it can be difficult to organize everyone's time such that they can attend the reviews. Making your reviews organized and helpful to the attendees might help them prioritize their calendars to attend the reviews in person.

Coping with Major Changes

There may be changes needed in your capacity plans that are outside of the normal day-to-day activities that your IT group pursues. Some significant changes require more rework and deeper analysis than the norm. In this section we investigate some reasons you might need to significantly rework one or more capacity plans.

Of course, the initial cause of major rework is the fact that you don't have any capacity plans at all! If you haven't begun this discipline of documenting plans for each of your major IT services and significant shared components, you have a lot of work in front of you. By now, you should have learned enough to create the first drafts and get them into a regular review cycle. The value of capacity plans becomes greater as you mature them through many review cycles, so begin to draft your plans now.

You shouldn't ignore the value you can get from early drafts. Even though you know that the capacity plan gets better as it matures, you should not withhold early versions from your organization. The maturity you're looking for comes only from the wide exposure of people who will really use your plan. Don't wait for perfection because it will never come while the plan is still private.

Another cause of significant new capacity planning work is the initiation of a new IT service. During the planning for the service, you should have defined enough information to establish an initial capacity and some projections of how quickly that capacity will be used. The initial capacity plan should document those along with some projections of when it might be time to grow beyond the capacity initially deployed for the service. You should expect the first capacity plan for any new service to be flawed. Having a plan that you can revise leads to much better plans over time. Starting with nothing ensures that you never move toward an accurate and useful plan.

Of course, the opposite of a new service is the discontinuation of an existing service. Frequently, capacity demands are shifted when a service is discontinued. For example, imagine that your organization has decided to stop using Websphere Application Server (WAS) as an application-enabling technology and starts insisting that all developers use Apache Tomcat instead. You will create a sunset plan that removes all instances of WAS while moving critical applications over to Tomcat. This causes rework to capacity plans for both services. Eventually, you will retire or convert the last of the WAS applications and will be able to retire the WAS capacity plan, which means that the Tomcat plan describes sufficient capacity for your needs. There are many scenarios in which you will update two plans to show that capacity of one type is decreasing while capacity of another is increasing.

Another scenario that can create big changes in your capacity plans is a technology change. For example, if your organization was using VMware to host virtual Windows® servers but decided to change to Microsoft as the virtualization engine, you'd be facing a technology change. Although this probably doesn't impact the services you provide to your business, it certainly impacts utilization and available capacity. Most likely you will need to use a different tool to measure utilization, and you probably will want to reassess the number of virtual servers you host per physical server. Those ratios will affect the total capacity available to host virtual servers. This same kind of scenario happens anytime you change the technology that provides capacity to your IT services. When these changes happen, you almost need to begin from scratch to create a capacity plan that makes sense.

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