Server farms are often made up of pools of resources, and with virtualization, the one-to-many relationship between physical and virtual capacity makes server resource allocation and capacity planning trickier than ever. Here are some simple guidelines to consider.
- Define business processes groups and the sub-system applications required to make them function. Typical application sub-system groups would include categorizations such as web servers, application servers, databases, administrative support, monitoring, email, and file serving.
- Create standardized: Virtual machine profiles that include not just guest operating system parameters and packages but also the applications required for each supported sub-system or groups of subsystems the operating system will support. Host server profiles defined to meet the requirements of anticipated combinations of virtual machine profiles. Storage types and sizing profiles to meet the expected demands of the applications to be deployed.
- Map the profiles to your business needs while developing critical resource thresholds that define both tolerable transient and longer term performance values. Use this exercise to define capacity replenishment triggers at which point new resources should be added. Always keep in mind the possibility of alternative mitigation strategies such as improved application efficiencies, reducing unnecessary traffic, and shutting down unused guest operating systems.
- Periodically monitor your resource demand, including current, peak, and forecasted values to evaluate whether your trigger criteria have been met. This should be done for both host systems and their guest operating systems. Accommodate acquisition and deployment lead times in your capacity plan so that solutions can be deployed before the overall performance of the virtual server farm becomes affected. Schedule these reviews to minimize the risk of unexpected surprises.
There are many challenges to deploying virtual systems. Using these few simple steps as a guide you should be able to create the foundation for a comprehensive policy.
