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Back to the Basics with Virtualization Capacity Planning

To be sure, there are plenty of new features to get excited about in vSphere 5.0. VMware has come a long way since 2002, when I first started using the technology. Often in the technology world, practitioners get excited about learning and implementing new technology without planning properly. They want to implement as fast as possible to bring about the benefits and innovation that the new technology has to offer. I believe that we have all been guilty of this at one point. So, this post is to remind all technology practitioners to take a step back and think about proper planning when implementing new technology projects. One of the basic tasks that should be done at the beginning of any virtualization design is capacity planning.

My role at TBL allows me to examine many virtual infrastructures. One of the common challenges that I see in many of these infrastructures is resource allocation after they have been running for a while. Workloads were virtualized quickly without proper capacity planning and by the team I am called in to assess the infrastructure, resources are strained in the environment. This point may come quickly if proper capacity planning is not performed up front. However, ongoing capacity planning must be performed periodically as moves, adds, and changes occur in the virtual infrastructure. Below are a few general recommendations for proper capacity planning:

  • Plan for performance, then capacity for production workloads – I have seen the opposite happen too many times to count. The storage capacity is planned for, but not the storage performance. Look at all workloads that will be virtualized. Measure the peak IOPS that will be required. Plan to fulfill the IOPS requirements, then add disks if necessary to meet the capacity requirements. This general approach will ensure a solid performance foundation.
  • Plan for peaks, not just averages – If you plan for averages, the environment may run OK until a performance spike is encountered. Then, performance may suffer for a critical workload. Think about things like month-end processing, student enrollment, or sales peaks. These times are when the environment needs the resources the most. Plan for the peaks accordingly.
  • Don’t forget about overhead – In a virtual infrastructure, there are some files and associated overhead required by the system to run the virtual workloads. These files may not seem like much by themselves, but in aggregate, they can add up to a lot. An example of something to plan for might be virtual machine swap files. In a vSphere infrastructure the virtual machine swap file size is the difference between the assigned memory and reserved memory for a virtual machine.

Ongoing capacity planning is needed as well to maintain a virtual infrastructure. This is where tools like vCenter Capacity IQ can help. Capacity IQ is capable of performing ongoing capacity planning, reporting, what-if scenarios and more. For example, if you want to see at what point you need to add more capacity in your infrastructure, Capacity IQ can model that based on your deployment patterns in the past. This is a very powerful analytic tool that can help you stay ahead of your capacity needs.

If we can plan from the beginning and utilize intelligent ongoing planning for capacity, then we can move from a reactive stance to a proactive stance while still being able to provide innovation quickly for the business. That’s a powerful combination. If you have questions about capacity planning, please feel free to contact me.