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Steps to Ease Data Center Cooling – Number 2

By Dave Cappuccio | March 25, 2012 | 0 Comments

Power and CoolingData CentersData Center Design

Cooling with the data center has become our achilles heal in many cases. Historically the folks in IT had relatively nothing to do with heat or cooling management, this was strictly under the purview of the facilities team (after all, if it wasn’t IT gear, it didn’t count). In todays world though the IT team has to get involved, since they are the ones that need to live with (and fix) the problem.

Well the good news is that in most older data centers (older being 10+ years), there are plenty of low hanging fruit to choose from when deciding what project to undertake in order to develop a more efficient cooling environment within the data center.

In this series of posts I’ll posit 10 of the easy steps you can take to solve, or mitigate the cooling issue at your site.

3. Ambient Temperature
Ambient temperature, or the average temperature in the data center, is often the easiest efficiency target, and often the one that is most often overlooked. Historically data centers were operated with room temperatures in the 68°F to 71°F range, primarily due to concerns about overheated IT equipment. These concerns were first developed by data centers during the mainframe era and have been carried forward to all data centers, regardless of equipment mix. However, todays server, storage and networking equipment have operating temperature variances that can easily exceed 95°F and still remain within the manufacturers guidelines.

Now we do not advocate running data centers at those high temperatures, but ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) has published it’s 2011 guidelines for data centers which recommend average ambient temperatures between 74°F and 80°F. Raising these temperatures can be one of the fastest ways to save operating costs there is, as studies have shown that raising the ambient temperature by 1°F can save upwards of 3% in energy costs. To obtain significant energy reduction while still maintaining a comfortable working environment Gartner recommends that data center operators consider an average ambient temperature of 78°F.

4. Hot and Cold Containment
The placement of racks within data centers has changed over the years, primarily due to an ever-increasing need to manage the heat exiting them. For the past 10 years or so the idea of hot and cold containment has become standard operating procedure (see 1 above). While this did not completely solve the heat problem, it did position the racks such that the hot air leaving one row would not immediately be drawn into the next row. Server administrators were still limited to how many devices to put into each rack though, as higher density racks would often create hot spots on the floor. These hot spots were then controlled by placing higher density racks across the floor space, essentially sharing their higher air temperature outputs with the rest of the floor.

Well designed data centers today have solved the hot spot issue by concentrating high density racks into hot or cold containment isles, rather than by spreading them around the floor. These aisles are designed so that all the heat leaving the racks contained within the row via walls, and then is quickly channeled upwards to the plenum, thus insuring hot air is “shared” with the rest of the data center. These hot containment zones can be constructed via sheet rock, heavy-duty plastic sheeting, or self contained units pre-designed by vendors. Hot or cold containment zones have two distinct benefits; the reduction of energy required to cool the data center floor through the elimination of heat leakage from the ends of rows, and the ability to fully utilize rack densities, allowing increased kilowatts per rack in the containment zones, thus increasing the usable rack space.

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