Cisco: Liquid Cooling For Computers Is Cool Again – Here’s Why

This is the third blog in my “The Future of Hardware” series which examines the impact of key industry trends and emerging innovations on the design and operation of computer systems. The first blog looked at the exponential growth in computing performance while the second looked at the trend of disaggregating computing components. This blog examines recent advances in cooling technology, specifically advances in liquid cooling for computing hardware.

Walk into any modern data center and the first thing you’ll probably notice isn’t what you see but what you hear – the unmistakable cacophony of coolers and fans humming all together to maintain ambient temperatures too. fresh as possible. But what you probably won’t see at a glance are plenty of other internal fans to the compute, networking, and storage systems that are also working hard to keep their many different components even cooler.

There is a simple reason for this. Like any machine (including your car), computers and their many components do not perform well when overheated. That’s why all computers and servers today are designed with an internal cooling mechanism (likely multiple fans) and room for airflow to keep internal ambient temperatures no higher than 115 degrees Fahrenheit. .

Air cooling has been around since the inception of computers, as evidenced by the air conditioning systems that were essential to remove heat from vacuum tubes in early models. With the advent of dense ICs, experimentation with cooling technologies has advanced with better air cooling, but also through a variety of alternative technologies, including liquid (water) cooling methods. But air cooling has been by far the most dominant cooling technology since the heyday of client/server computing, with liquid cooling largely relegated to high-performance computing and other more specialized systems.

But all that may be about to change…

Why liquid cooling is back in fashion

The reasons for the renewed attention and interest in non-air-cooled technologies can be found in two previous blogs in my “Future of Hardware” series. First, I wrote about the rapid growth of computer performance metrics such as chip/socket density, memory and storage capacity, and associated power requirements. Second, I discussed the trend toward disaggregation of computer components (especially memory), which will likely lead to the development of more processing-intensive computer systems. In turn, these next-gen systems will require more heat dissipation than traditional fans and airflow may not be able to handle properly.

This is one of the reasons for all the buzz within the computer and data center industry about advanced cooling technologies such as microchannels and a host of computer liquid cooling techniques. The idea is that with better cooling, computers can be much more powerful, which can lead to accelerated innovations. In many ways, it’s a search for the holy grail within the IT industry, and many companies, including Cisco, are actively involved in it.

I’ll focus the rest of this blog on liquid cooling, which Cisco has sought to evaluate in close collaboration with our vendors. Over time, I predict liquid cooling will evolve from a domain largely reserved for DIY PC enthusiasts to mainstream technology found everywhere in data centers. There are still a lot of details to iron out, including which liquid cooling technique might win out (think VHS versus Beta or HD-DVD versus Blu Ray).

In the mix are technologies such as single-phase and two-phase immersion, which cools by literally submerging computer components in liquids. Another technology is liquid cooling based on single-phase and two-phase cold plates, which transfers heat through a cooled connected heat exchange system by moving liquid through it.

Regardless of which technology reigns supreme, there are many compelling reasons to embrace liquid cooling in general. Here are a few:

  • Some of the research I’ve seen indicates that liquid technology can provide 60% better cooling than comparable air-cooled designs achievable using a 2RU rack chassis.

  • Liquid cooling promises to be more durable as it uses less electricity than air cooling to drive the internal fans.

  • This can help meet energy use efficiency (PUE) standards, which are becoming more stringent. For example, Shanghai, China has set guidelines for a benchmark PUE of less than 1.3, well below the 2.2 PUE that most data centers in China run.

  • It can help modernize data centers to meet Global Warming Potential (GWP) goals for various emissions through smaller, more efficient builds. Currently, data centers account for 1.8% of electricity consumed and 0.5% of greenhouse gas emissions in the United States alone.

Positive impact for UCS

These developments are nothing but good news for hardware designers, including those of us working on Cisco UCS. When we launched the X Series, we pitched it as a system designed for the next decade of computing design and operation. This includes the ability to integrate new and emerging technologies, including better cooling systems, especially liquid cooling. Some of the most interesting projects underway are:

  1. Prototype of a cold plate (heat exchange) solution for individual UCS servers

  2. Evaluation of rack-level cooling distribution units (CDUs) that can provide heat exchange for each server in the rack

Although these projects are experimental at the moment, I anticipate that they will soon become mainstream. As with most things involving computer technology, there will be a measured and incremental evolution in terms of innovation and adoption. Specifically, I expect data center coolers to stay up for a while, even if rack CDUs are installed. Over time, CDUs themselves will evolve and grow as centralized units at the data center level (like the evolution of power distribution systems) that will revolutionize the way data centers are designed. and populated. Eventually, data center operators will consider even more extreme liquid cooling methods, including complete system immersion.

Downstream and ancillary effects can be equally compelling. Not only will we be able to build more energy efficient and environmentally friendly servers and data centers, but we will also enable the next generation of computing solutions. This includes converged infrastructure and hyperconverged infrastructure that can run more workloads and support more applications using less power and footprint possible today.

Stay tuned for more as this hardware future isn’t as far off as you might think.

about liquid cooling and the future of computing.


Future of Hardware blog series:

  1. Current advances in computer hardware may propel the next generation of “Moonshots”

  2. Memory decay is perhaps the most exciting trend in computer system design right now.

Podcast interview on Data Center Knowledge