Server virtualisation is already saving you money. So why not save some more? Forrester Research shares thee recommended changes.

As the global economy is recovers, pent-up business demand for new apps and market initiatives is driving server investments. Forrester finds that 25 percent of organisations expect server spend to grow by 5 percent to 10 percent, and 6 percent expect it to grow by 10 percent or more. And to reduce operating and capital costs, improve disaster recovery, and accelerate time-to-market for new apps, organisations are turning to server virtualisation.

But a new motivator to expand and improve the use of server virtualisation is bubbling to the surface: reducing energy consumption. Why? Forrester finds that there are three primary motivators:

  • Financial. The costs to power and cool a server over its life may actually exceed its purchase price. Virtualisation reduces the overall energy consumption of your server footprint, thereby allowing the same workload to run on fewer physical, energy-consuming servers.
  • Resiliency. To ensure that uptime and service-level agreements are maintained, virtualisation alleviates out-of-space, power, and cooling constraints.
  • Green. Virtualisation reduces the overall server footprint and cuts energy-related carbon dioxide emissions as well as the electronic waste from purchasing and then disposing server equipment in the future.

To cut server energy costs by up to 65 percent and exploit your energy savings potential from virtualisation, Forrester recommends three process improvements:

1. Increase your overall virtual-to-physical server footprint

There are significant opportunities for organisations to increase their overall virtualisation footprint across all server environments and platforms. We found that, while approximately 90 percent of firms are virtualising or planning to virtualise their servers, only 37 percent of their x86 operating system instances are virtual servers. In two years time, this is expected to increase to 65 percent.

Additionally, the extent of virtualisation varies significantly based on the server environment, and the platform. The first step to maximising energy savings is to increase the overall virtualisation footprint across all environments and platforms. To ensure you're actually saving energy, be sure to turn off or decommission servers that are no longer running any workloads. Forrester's Green IT maturity assessment methodology prescribes the following virtualisation targets to achieve one of four levels of green IT maturity:

  1. Needs improvement (1 percent to 25 percent virtualised);
  2. Improving (26 percent to 50 percent virtualised);
  3. Robust (51 percent to 75 percent virtualised); and
  4. Best-in-class (76 percent to 100 percent virtualised).

2. Maximise your virtual machine to physical host and utilisation ratios

Virtualisation alone is not enough. In addition to increasing the overall server virtualisation footprint, drive additional energy savings by virtualising more efficiently. Server virtualisation ratios are not keeping pace with modern hardware and virtualization platform capabilities. It's common to break even on the purchase of a new server with a 4-to-1 virtual machine (VM)-to-physical host ratio, but most servers can accommodate 15 VMs. Virtualising more efficiently can help you avoid three new server purchases, not to mention the additional power, cooling, and space expenses from this new equipment.

A key ratio that administrators use to determine the acceptable number of VMs per physical host is server CPU utilisation. There is a direct relationship between CPU utilisation, VMs per physical host, and energy savings. A standalone unvirtualised server might run at an average of 10 percent to 15 percent utilisation, whereas virtualised servers could theoretically approach 100 percent.

However, Forrester finds that most administrators are hesitant to push the utilisation of their physical host servers beyond 25 percent to 50 percent - limiting both the number of VMs per physical host and energy savings potential. Underutilised servers still consume considerable amounts of energy.

If you increase the number of VMs per physical host, you can decrease the total number of physical servers and reduce energy consumption. As server teams become more comfortable with higher server virtualisation utilisation ratios, they can safely add more VMs per physical server without diminishing service levels.

3. Source more energy-efficient servers and architectures

Sourcing more energy-efficient servers and architectures may be your only remaining option to reduce energy consumption if you've maxed out virtualisation ratios or realised that you're going to need higher-end server infrastructure.

Energy consumption will be higher on a per-server basis - but total server energy consumption will be lower due to the reduced number of overall servers. If your risk tolerance doesn't allow you to push the limits of virtualisation ratios, then these more efficient server environments may be your only viable option.

Forrester recommends seeking newer models of the same servers your organisation already purchases. The simple act of server refresh will reduce server energy consumption. New server architectures, such as blade systems and converged infrastructure, are not only more energy-efficient by nature but also facilitate aggressive virtualisation.

The energy savings can be impressive, as noted by a VP of an online services company who said about his converged architecture: "We achieved 70 percent space savings, 25 percent operational expense savings, 30 percent to 40 percent heat dissipation improvements, and 40 percent power savings."

Doug Washburn is an Analyst a Forrester Research, where he serves Infrastructure and Operations professionals.