Energy Efficiency Guide: Assessment

Data Center Energy Efficiency Guide: In developing a plan to improve the energy efficiency of your data center, the first step is to gain an understanding of the current conditions. Here are tips on simple fixes to common problems that can provide short-term improvement without huge expense.

Rich Miller

March 4, 2011

4 Min Read
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In developing a plan to improve the energy efficiency of your data center, the first step is to gain an understanding of the current conditions. Where are you doing well? What areas need improvement? And perhaps most importantly, where are the "low-hanging fruit" - the simple fixes to common problems that can provide short-term improvement without huge expense. So we start our journey with some guidelines on assessing your data center, and addressing quick fixes.

Turn Off Unused Servers
A surprising amount of energy can be saved simply by turning off unused servers. You might think every server in a data center is tightly managed. You'd be wrong.  These "vampire"servers continue to live on and consume energy.

A 2010 survey (PDF) conducted by The Green Grid found that nearly a third of participants - who presumably would be among the most efficiency-conscious operators - have not attempted o discover whether they have servers that are unused.Of the companies that  have investigated, 35 percent found that between 5 and 25 percent of their servers were not being used.

The Green Grid estimates that the average cost of powering a server for a year is $250. Thus, a data center with 5,000 servers and 5 percent idle would be spending $62,500 for energy to power servers that are doing nothing. Then there's the hardware savings of using fewer servers. "Ultimately, finding unusued servers could avoid the cost of a new data center," The Green Grid concluded. "Even a small percentage of servers is an expensive problem to ignore."

So how do you deal with unused servers? In a 2007 study, two major computer manufacturers found 500 servers with no know function.  The systems were turned off and kept in place for 90 days. If someone came forward to claim a server, it was put back into service. If no complaints emerged after a quarter, the servers were removed. Once the process is complete, implement a repeatable mechanism to identify unused servers.

Plug the Leaks
Managing the airflow and air pressure are key steps in improving the energy efficiency of your data center. When you'r epaying to cool the air, you want to ensure that the coolr air reaches the servers and does its work. Many data centers fail to take simple steps to eliminate "leaks" in the pathway between your computer room air conditioners (CRACs) or air handlers (CRAHs) and the racks containing your servers. There are a number of areas along this route where blockages, gaps and recirculation can diminish air pressure and temperature, making your mechanical systems work harder to cool the space. Here's a list of tips from the Energy Star program at the U.S. Environmental Protection Agency:

  • Eliminating sub-floor obstructions can improve efficiency. Many data centers use the sub-floor plenum for more than just airflow. Cabling, for instance, can impede proper air circulation, and taking fixed obstructions into account can yield a more efficient floor tile arrangement. A physical examination of the entire plenum can reveal blockage issues that can be easily addressed to improve efficiency.

  • Floor grommets can improve cooling efficiency by sealing areas where cables enter and exit plenums, such as a raised floor. Grommets fit into cutouts in the floor and direct cabling through brushes or fitted openings that provide a tight seal, preventing air from escaping around the cables. Less leakage helps direct more cold air to the equipment that needs cooling.

  • Vented tiles are incorrectly located or sized in many data centers. Due to the complexity of airflow behavior, the correct configurations are not readily obvious. A professional air flow assessment can help indentify ways to improve cooling efficiency.

  • On the front of server racks, unused rack spaces (open areas) often allow cool air to bypass the equipment. Blanking panels are fundamental to efficient airflow, covering open areas so that air passes through the equipment rather than around it. Blanking panels decrease server inlet air temperatures as well as increase the temperature of air returning to the CRAC, both of which improve operational efficiency. Adding a single 12-inch blanking panel to the middle of a server rack can yield 1 percent to 2 percent energy savings.

  • Structured cabling systems can eliminate disorderly and excess cables that might constrain exhaust airflow from rack-mounted equipment. In addition, cutting cables and power cords to the correct length will provide more room for air to flow away from the back of the rack.

These recommendations provide a good starting point on your energy efficiency project. Now let's talk servers.

Next Up: Processors and Servers

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