Closed-Loop Cooling Explained: The Plumbing Behind Meta’s AI

One of the consequences of the AI boom is that cooling servers has become a serious engineering challenge.

The more powerful the AI hardware becomes, the more heat it generates during operation. And at a certain point, simply blowing more air through a server rack stops being a particularly efficient method of cooling.

That’s why when I visited Meta’s AI Infrastructure in Texas, one of the technologies I was most interested in wasn’t actually the AI hardware. It was the plumbing.

The Cooling Shift

Traditional data centers, that’s data centers used for compute tasks such as searching for your favorite creator on Instagram or liking a post on Facebook, will more often than not use air cooling to keep the hardware at an optimal temperature. 

Even a few years ago, using air cooling methods to cool AI hardware was an achievable solution. In fact, I visited a data center in Altoona, Iowa, where racks of 16 Nvidia H100s were kept cool completely through air cooling with minimal water usage. Minimal amounts of water were used at the start of the data center cooling process to cool the air during warmer months, but no water was ever being sent directly to the hardware.

It’s only more recently that newer AI hardware designs have created the demand for a newer, more optimal method of cooling.

Enter closed-loop liquid cooling.

There’s a common misconception that AI data centers are automatically big water users. The reality depends on the cooling design — Meta’s data centers use a closed-loop system that recirculates water in a sealed loop, using very little on an ongoing basis.

The majority of Meta’s newest AI-optimized data centers use closed-looped, liquid cooling as it is the most efficient way to cool GPU servers — both from a resources point of view, but also from an infrastructure point of view.

What Is Closed-Loop Cooling?

The basic idea behind closed-loop liquid cooling is actually pretty simple.