The process encompasses:

• The monitoring of performance and throughput of IT services and the supporting infrastructure components.
• Undertaking tuning activities to make the most efficient use of existing resources.
• Understanding the demands currently being made for IT resources and producing forecasts for future requirements.
• Influencing the demand for resources, perhaps in conjunction with Financial Management.

The production of a Capacity Plan enables the IT service provider to deliver services of the quality defined in Service Level Agreements (SLAs). As shown in Figure 1, Capacity Management is essentially a balancing act:

• Cost against capacity: Ensuring that the processing capacity purchased is not only cost-justifiable in terms of business need but also making the most efficient use of those resources.
• Supply against demand: Ensuring that the available supply of processing power matches the demands made on it by the business, both now and in the future. It may also be necessary to manage or influence the demand for a particular resource.

Why Capacity Management?

Capacity Management is sometimes viewed as an old-fashioned, mainframe-oriented discipline. IT Services Managers overseeing distributed computing facilities have argued that Capacity Management takes more time, effort, and therefore cost, than it is worth, suggesting it might be better to pay for upgrades as needed. IT organisations with this perspective often exhibit the following symptoms:

• Procurement of IT equipment is justified on an individual capital return basis, rather than addressing the overall corporate requirement.
• There are no corporate Capacity Plans.
• No business Capacity forecasts are produced.
• Network Capacity Management is conducted reactively.
• Capacity Management of servers is also handled reactively, albeit less often.
• Little or no Capacity Management is performed on desktop equipment.

Managing the capacity of large networks of distributed equipment is more complex than in the ‘good old days’ of the mainframe. For all thriving organisations, the financial investment in IT is increasing, making it even more critical to plan for growth. While the cost of upgrading a component in a mainframe environment is substantial, there are often many more components in the distributed environment that need to be upgraded. Additionally, economies of scale might reduce the cost per individual component when multiple components are purchased. Therefore, Capacity Management should contribute to the process to ensure the best deals with suppliers are negotiated.

A corporate Capacity Management process ensures that the entire organisation’s capacity requirements are met. The cost of upgrading all the desktop equipment in an organisation could easily exceed the cost of a mainframe upgrade. Capacity Management should be responsible for the ‘refresh policy’, ensuring that desktop equipment has sufficient capacity to run the applications that the business requires for the foreseeable future.