Datacenter design is undergoing a significant transformation. The fundamentals of the datacenter -- servers, cooling systems, UPSes -- remain the same, but their implementations are rapidly changing, thanks in large part to the one variable cost in the server room: energy.

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Still in its infancy, though growing up fast, server virtualization is increasingly being relied on as a power-saving outlet for enterprises rolling out cost-effective datacenters or retrofitting existing datacenters to cut power costs considerably. What may come as a surprise, however, is that hidden energy costs await those who do not plan the layout of their virtualized datacenter wisely. And the chief culprit is heat.

Consolidating the workload of a dozen 1kW servers onto one 2kW machine means that most virtualization hardware platforms produce more heat per rack unit than individual servers do. Moreover, collecting several virtualized servers into a single, high-density rack can create a datacenter hotspot, causing it and adjacent racks to run at significantly higher temperatures than the rest of the room, even when the room is centrally cooled to 68 degrees. Blade servers are notorious for this because they run extremely heavy power supplies and tend to move an enormous amount of air through the chassis. Virtualizing them will indeed significantly reduce datacenter energy costs, but it won’t provide a complete solution for reining in your datacenter’s energy needs. For that you have to retrofit your thinking about cooling.

Cooling on demand

For the most part, big beefy air conditioning units that push air through drop ceilings or raised floors remain regular fixtures in the datacenter, but for enterprises building out for energy efficiency or seeking to retrofit for added energy relief, localized cooling -- mainly in the form of in-row cooling systems -- is making a splash.

“We originally designed our in-row cooling solutions to address hotspots in the datacenter, specifically for blade servers, but it’s grown far beyond that,” says Robert Bunger, director of business development for North America at American Power Conversion (APC). “They’ve turned out to be very efficient, due to their proximity to the heat loads.”

Bucking the “big air conditioner” paradigm, in-row cooling systems such as APC’s are finding their place between racks, pumping out cold air through the front and pulling in hot air from the back. Because cooling is performed by units just inches away from the source rather than indiscriminately through the floor or ceiling, datacenter hotspots run less hot. What’s more, rather than relying on a central thermostat, these units function autonomously, tapping temperature-monitoring leads placed directly in front of a heat source to ensure that the air remains within a specified temperature range. If a blade chassis starts running hot due to increased load, the in-row unit ramps up its airflow, dropping the air temperature to compensate.