Capacity planning estimates space, hardware, software, and connection infrastructure resources needed over a future period of time. It is a process that predicts timing, quantities, and types of resources that will be needed within an infrastructure. It determines the future configuration of hardware and software for a network. Capacity planning ensures the system will be able to support anticipated performance demands and handle a certain user load.

                A typical capacity planning concern is whether the resources will be available to handle an increasing number of user load.  A good capacity plan is making sure the IT infrastructure is scalable.  It is in the best interest of the organization to implement an IT infrastructure that will consider capacity growth at the beginning of a system launch. It would be more expensive to try to upgrade equipment and networks after the system has already been implemented. Capacity planning aims at planning so well that new capacity is added just in time to meet the anticipated need but not so early that the resources will go unused for a long time.  Ensuring adequate capacity involves:

·         The type of resource capacities required, such as servers, disk space, or bandwidth

·         The timing of when the additional capacity will be needed

·         The size and quantities of the resources needed

·         The decisions about capacity that are based on the forecasts of anticipated user load

With the emergence of new technologies and business strategies and forecasts changing, capacity planners must always revisit their capacity plan.

        Not planning well leads to not having enough capacity. Not having enough capacity leads to performance issues. Analysts acknowledge the importance of adequate capacity planning but a lot of times it is not done well. Some of the reasons why many infrastructures fail at effective capacity planning are:

·         The analysts are too busy with other activities, such as day-to-day activities

·         The users lack interest in predicting the future user loads

·         The users who are interested in predicting the future user loads can’t forecast accurately

·         The capacity planners may not be using the right measuring tools

·         The planning part is not a typical part of infrastructure culture

·         The managers will sometimes confuse capacity planning with capacity management

           There are numerous capacity planning tools in the market to help organizations plan and forecast better. There are no one size fits all capacity planning tools because not all infrastructures are the same or have the same system requirements.  For example, Windows 2000 Active Directory Sizer (AD sizer), this tool gives you an estimate of the hardware you will need based on the user load and other objects that will be stored. These tools should help organizations avoid risk and reduce cost. There are some tools used to monitor and analyze the performance of the current hardware and software. There are also analytical modeling tools to help with “what if scenarios.” These tools give you a number of possibilities that can be explored. The best tools are the ones that are seen to be scalable.