Facebook says the Oregon location for its new data center is perfect for using outside air to cool its servers, a key element of its efforts to make its infrastructure more energy efficient. But Facebook's next huge data center will be built in North Carolina, where the climate is considerably warmer.

Rather than reducing its reliance on air economizers, Facebook plans to run its future data centers at warmer temperatures. The company said the decision was based on testing at its new Prineville, Oregon facility.

85 Degrees in the Hot Aisle

"Our teams have learned a number of things over the past few months of operation, which have led to changes in our second phase of Prineville as well as our new data center in Forest City, North Carolina," wrote Yael Maguire on the Facebook blog. "Comparing our first phase of Prineville with how we plan to operate Forest City, we've raised the inlet temperature for each server from 80°F to 85°, 65% relative humidity to 90%, and a 25°F Delta T to 35°. This will further reduce our environmental impact and allow us to have 45% less air handling hardware than we have in Prineville."

The Delta T is the difference between the temperature in the cold aisle and hot aisle, meaning the hot aisles in Facebook's new data center space will be as warm as 120 degrees - not a pleasant work environment for data center admins. Mindful of this, Facebook designed its Open Compute Servers with cabling on the front of the server, allowing them to be maintained from the cold aisle rather than the hot aisle. The contained hot aisles in Prineville are unlit, as the area was not designed to be staffed. See our video, Inside Facebook's Server Room, for more details.

Warmng Trend - For Some

Historically, most data centers operate in a temperature range between 68 and 72 degrees F (20 to 22 degrees C). In recent yearslarge data center providers and industry groups have advocated increasing the data center temperature to 80 degrees F (about 27 degrees C).

Raising the baseline temperature inside the data center – known as a set point - can save money spent on air conditioning. By some estimates, data center managers can save 4 percent in energy costs for every degree of upward change in the set point. But nudging the thermostat higher may also leave less time to recover from a cooling failure, and is only appropriate for companies with a strong understanding of the cooling conditions in their facility.

The leading U.S. industry group for heating and cooling professionals, ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) increased its recommended operating range for data centers from 77 degrees to 81 degrees in a 2008 update. But recent data from end users indicates that few enterprise data centers are raising their temperatures.

More Open Compute News

Facebook also shared several other updates from its Open Compute Project: