Nov 18 2011

Capacity Planning in Virtual Environments

This is my final post highlighting the white papers that I did for SolarWinds. This one focuses on a white paper titled “Capacity Planning in Virtual Environments” which is a topic that is often not very well understood or executed in virtual environments. Capacity planning can be a real challenge in virtual environments and there is a lot more to it than meets the eye, below is an excerpt from this white paper, you can register and read the full paper over at SolarWinds website.

Virtualization is all about the sharing of resources. You have to plan with the big picture in mind and take into account your virtual environment as a whole. A balance of resources is critical in a virtual environment since the server hardware used for virtualization is bigger and more expensive than traditional server hardware as it has to support many virtual machines (VMs) running on it. If resources are unbalanced on a host, it can lead to wasted resources, and since the whole point of virtualization is to make the most efficient use of all resources, this goes against the reasons that we virtualize in the first place. For example, if a host runs out of physical memory, it limits the number of VMs that can run on that host despite having plenty of other resources available to it. Sure, you can use memory over commitment, but performance severely degrades once your VMs start swapping to disk to make up for the lack of physical host memory. As a result, the lack of having enough physical memory available for VMs means that you are wasting resources and money.

Trying to keep your resources balanced isn’t all that simple; you need to look at historical resource trends and usage to determine what that balance point is. Trying to calculate this manually is almost impossible. You need tools that can analyze your historical data and report how your environment has grown over time, how it stands today and how it will look in the future. Another area that further complicates resource calculations is spare capacity. If you are using High Availability in your environment, which most companies do, you have to maintain sufficient spare capacity to handle the load when host failures occur. So, you need a pool of resources that is unused at all times so you have enough resource capacity to handle VMs from failed hosts. Trying to factor spare capacity into your resource calculations can quickly get complicated, having a tool that can do this for you can make it a much easier exercise.

Full paper available here

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