How to Manage Capacity in Virtualized Environments

Alternatives for managing capacity in dynamic virtual environments

Regardless of the practices and technologies used, the ultimate goal for capacity management is to balance IT supply with demand while maximizing efficiency and predictability. Fundamentally, it's about developing capacity intelligence by understanding the following four things:

1. How much capacity you have (current/future, used/free)

2. How the capacity is being used (by whom and when)

3. How much capacity you will need (current/future)

4. When you will run out of capacity

Given the challenges and considerations in a fluid virtual environment, this capacity intelligence needs to be closely tied to the virtualization layer and delivered as real-time as possible.

Capacity management approaches

There are many approaches to capacity management but, generally speaking, there are three different approaches: rule of thumb, homegrown solutions or purpose-built tools.

Approach No. 1: Rule of thumb

Rule of thumb involves guesstimates based on past experience. For example, in the past, four VMs can generally run on one core, so going forward the same assumption is used. Obviously there are serious drawbacks with this approach in a dynamic environment, including inaccuracy and the inability to establish a systematic process around this approach.

Approach No. 2: Homegrown solutions

Homegrown solutions include scripts and spreadsheets. This is a more systematic approach than rules of thumb and, in the case of scripts, it may work in larger enterprises with sophisticated IT skills. However, this approach can quickly become expensive and time-consuming to maintain—and may also be inaccurate, especially with a rapidly changing infrastructure. In a virtual environment, there are many intricacies in how VMs interact with the layers of infrastructure, so it is hard to do this right with a great amount of expertise.

Approach No. 3: Purpose-built tools

Purpose-built tools are the preferred approach for a virtual environment because they take the guesswork (and much of the labor) out of collecting and maintaining capacity information in a constantly changing environment. Perhaps most importantly, tools that are closely integrated with and aware of the virtualization layer can provide highly-reliable and real-time intelligence.

With the right tool and process in place, IT administrators will have automated, real-time capacity intelligence to make day to day and strategic capacity management decisions in a virtual environment.

Rob Smoot is a Group Product Marketing Manager at VMware. Prior to VMware, Rob held various positions in product management, strategic planning and sales operations at Veritas Software, and was a management consultant at Andersen LLP. Rob graduated from Brigham Young University, and received a MBA from Wharton at the University of Pennsylvania. He can be reached at rsmoot@vmware.com.