Windows capacity planning: Juggling user demand with system resources

Major upgrades such as Windows Vista and Microsoft Exchange Server 2007 can be especially taxing on a system, so it's important to do the proper capacity planning ahead of time. IT management expert Harris Kern offers nine steps to creating a successful Windows capacity plan.

Harris Kern
If you think it is hard to juggle capacity resources with user demands now, just wait until your organization upgrades to Microsoft Vista or Exchange 2007 or SQL Server 2005 because these applications are going to tax your system even more. Your best course of action is to start Windows capacity planning now for these big upgrades.

You have to have a plan that ensures IT resources are available just before they are needed -- a "just-in-time" approach to resource management -- and that's a tough nut to crack when you're dealing with multiple mission-critical Windows servers with multiple server rooms.

Here are the nine steps that will help you create a Windows capacity plan:

  1. Define the scope of production
    Define which of your Windows production systems are mission-critical and non-mission-critical. Sometimes it can be a tough call: Obviously, Microsoft's operating system is mission-critical, but what about the WAN and storage supporting your production applications (i.e., HR, order entry, manufacturing, etc.) along with their associated data bases (Oracle, SQL Server 2005 and so on).

  2. Identify key resources to be measured
    This determination is made based on current knowledge about which resources are most critical to meeting future capacity needs. These resources could revolve around:
    • Server disk space
    • Network bandwidth
    • CPU utilization
    • Memory utilization
    • Backup/Restore requirements
    • Web server
    • Database performance
    • Uptime
  3. Measure the usage of the resources
    Now you can measure the resources listed above in terms of their performance or usage. These measurements provide two key pieces of information. The first is a usage baseline from which future trends can be predicted and analyzed. The second is the quantity of excess capacity available for each resource. For example, a Windows database server may be running at an average of 60% utilization during peak periods on a daily basis. These daily figures can be averaged and plotted on a weekly and monthly basis to enable trending analysis.

  4. Track usages to maximum capacities
    The intent here is to determine how much excess capacity is available for selected components. The utilization or performance of each measured resource should be compared to the maximum usable capacity. Note: The maximum usable capacity is almost always less than the maximum possible. The maximum usable server capacity, for example, is usually only 80% to 90%. Similar limitations apply for network bandwidth and cache storage hit ratios. By extrapolating the utilization trending reports and comparing them to the maximum usable capacity, it should now be possible to estimate at what point in time a given resource is likely to exhaust its excess capacity.

  5. Collect workload forecasts from managers
    You'll want to collect information such as the number of concurrent users, remote network requirements, number of servers required and desktop network requirements. For example, during peak hours, you want to…

  6. Transform forecasts into resource requirements
    After collecting the workload forecasts, the projected changes need to be transformed into resource requirements. They will also allow you to project the estimated time frames at which workload increases will occur.

  7. Map the requirements onto existing utilizations
    The projected resource requirements derived from the workload projections of the users in step #6 are now mapped onto the charts of excess utilization from step #4. This mapping will show the quantity of new capacity that will be needed by each component to meet expected demand.

  8. Predict when the Windows resources will be out of capacity
    Mapping the quantity of additional capacity needed to meet projected workload demands will also pinpoint the time frame at which these upgraded resources will be required.

  9. Update Windows usages and forecasts
    Capacity planning is not a one-shot event but rather an ongoing activity. You will derive maximum benefit from continually updating the plan and keeping it current.

Harris Kern is the author of 44 IT and self-help books. He is recognized as the foremost authority on providing practical guidance for solving IT management issues. Harris is the founder behind Harris Kern's Enterprise Computing Institute and the best-selling series of books published by Prentice Hall. The series includes titles such as IT Services, IT Organization and CIO Wisdom. Harris can be reached at harris@harriskern.com.

This was first published in April 2007

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