Airflow management 101: Active or passive exhaust?

Airflow management 101: Active or passive exhaust?

There are cases in which active or passive cooling will work better in your data center.

Cooling accounts for a staggering 40 percent of all power consumption in the data center. It's a problem that some of the world's technology leaders such as Google, Facebook and Microsoft have attempted to address in a variety of unique ways – under-water server rooms, open-air facilities that use nothing but wind and the morning air to cool down and much more.

But even these novel methods are relatively rare and expensive to implement. There are simpler and more cost-effective ways to save money on data center cooling right now. The best place to start is with improving airflow management through proper exhaust containment.

Bypass airflow: The scourge of data center cooling

Bypass airflow is arguably the most notorious culprit for wasted cooling capacity. Despite data center managers' claims that they need more cooling capacity to support their higher-density environments, more often than not, they really need to improve airflow management.

In some cases, these enhancements are cosmetic. Maybe cables need to be rearranged to ensure airflow isn't being blocked, or your top-of-rack switches need additional hardware to maintain front-to-back cooling. But other times, the issue is symptomatic of a more fundamental fault: Using an active airflow setup when you should be using passive, and vice versa.

What's best for your data center?

"It really comes down to the needs of your data center."

Should you use an active or passive airflow system? The answer is "it depends."

There are some cases in which a passive exhaust system can adequately maintain allowable temperatures using less energy than an active containment system. At the same time, passive systems rely almost entirely on server fans to ensure that cool air actually reaches the equipment and that exhaust does not mingle back into the cold aisle, which means even a slight airflow obstruction can lead to serious issues. 

Active exhaust, on the other hand, adds more airflow muscle to the mix to alleviate strain on server fans. This also means more energy consumption.

In other words, one isn't always better than the other. Instead, selection must ultimately come down to the unique specifications of your data center.

To help make your decision, the infographic below outlines the differences between active and passive air, the benefits of each and what type of environments they perform best in.