CDC UNIFIED PROCESS
PRACTICES GUIDE
CAPACITY PLANNING PRACTICES GUIDE
UP Version: 06/30/08 Page 1 of 4
Purpose
The purpose of this document is to provide guidance on the practice of Capacity Planning and to
describe the practice overview, requirements, best practices, activities, and key terms related to these
requirements. In addition, templates relevant to this practice are provided at the end of this guide.
Practice Overview
Capacity is defined as the maximum amount or number that can be received or contained. For example,
the amount of data that a computer hard disk can store is the disk’s capacity. The maximum possible data
rate received over a communication channel under ideal conditions is its capacity. Capacity can also refer
to non-technical things such as the maximum amount of work that an organization is capable of
completing in a given period of time or the maximum number of people that can physically occupy a
room.
Discrepancies in capacity and demand results in inefficiencies associated with either under-utilized
resources or unmet user demand. The goal of capacity planning is to minimize this discrepancy and to
provide satisfactory service levels in a cost-efficient manner. The Information Technology Infrastructure
Library (ITIL) defines capacity management as supporting the optimum, and cost effective, provisioning of
services by helping organizations match their resources to the business demands.
Capacity planning doesn’t always mean planning for periods of peak demand. Capacity requirements can
vary greatly from times of peak demand to times of limited demand. As a result their may be drastic
differences in the resources required to maintain normal operations during periods of peak demand.
When planning for what levels of capacity will be supported it’s important to understand and weigh the
costs, benefits, and risks of delivering, or not delivering, certain level of capacity. Because of this,
capacity planning is more of an art than a science.
Depending on the type of project, it’s possible that true capacity planning may play a small role in the
overall project life cycle. For example, assume a project is only responsible for creating a small database
application that will be stored on a shared server within a data center. The server’s capacity is the
responsibility of the data center manager. The project manager may not have any real control over the
server at all. However, the project manager is responsible for ensuring that the business requirements are
met. For example, if it is required that the database be accessible 100% of the time the project manager
needs to ensure this is the case. Accomplishing this requires working closely with the capacity provider.
The data center manager would then be responsible for maintaining adequate server capacity to fulfill the
business need.
Capacity planning is simpler if an existing system is in place and needs only adjustments to meet current
or expected changes in capacity. However, when planning capacity for a new system, analysis of
information such as historical project archives, industry standards, and information obtained from
vendors/customers, etc. can assist in estimating expected demands upon that system. Regardless of
which situation a project is planning for three basic steps for capacity planning include:
1. Determine capacity requirements by understanding what work will be performed by the system and
then quantify the user experience as it relates to that work
2. Analyze current capacity to determine how it is meeting the requirements of the system and needs
of the users
3. Plan for future capacity by forecasting future business activities and system requirements.
Implement required changes to ensure sufficient capacity to meet demands upon the system
Determine Capacity Requirements
1. Define required system performance to support associated business and process workloads.
Capacity planning defined in business terms rather than utilization of CPU, memory, hard drive
