In the quest to maintain optimal operating temperatures while meeting the increasing computing densities through server racks, organizations find themselves torn between air and liquid cooling facilities. This article will walk you through both facilities to help bring clarity.
As the data centres continue to add more computing power through compact server racks to accomplish intensive workloads, such as advanced analytics and AI, server racks will generate more heat, making it difficult for cooling systems to keep up with efficient operations. In early times, the rack server requirements were below 20 kW, so the data centres could rely on air cooling to maintain operating temperatures. But today’s high-performing racks go beyond forcing organizations to seek efficient solutions like liquid cooling. But there are many factors to consider between air and liquid cooling facilities to see which is right for you.
What is Air Cooling?
Data centres have been employing air cooling since the beginning and continue to do so. With time, cooling systems evolved to be more efficient. These systems use fans to blow cool air that circulates around the hardware dissipating the heat. There are three types of air-cooling systems: room-based, row-based and rack-based. And the difference between them lies in the way they control airflow.
In room-based systems, air is circulated in the server room or heat is dissipated through vented tiles. The latest room-based cooling systems feature hot and cold aisles to facilitate better airflow. In a row-based system, each row comes with a dedicated cooling unit to target specific equipment, resulting in high cooling efficiency and less power requirement.
The rack-based system employs dedicated cooling units to each server rack and thus offers better precision and efficiency than its counterparts. However, this makes the system more complex because of numerous devices.
Air cooling is invaluable for data centres’ equipment. It is easy to maintain and use. As a result, it is deployed highly in data centres.
What is Liquid Cooling?
Liquid cooling systems help address the limitations of air-cooling systems regarding the requirement of high computing densities. One of the liquid cooling technologies is direct-to-plate cooling, wherein a cold plate is placed next to the component such as CPU, GPU or memory card and small tubes are connected to a plate carrying cold water and discarding warm water in a circular motion.
A similar concept is applied at the rack or server level. Water or any coolant is circulated in a closed loop to dispute heat. However, the process varies from one solution to the next. Some use a contained coolant, an exchanger to dissipate heat and a mechanism to maintain coolant temperature as it circulates. An exchanger can be mounted on the back of the server rack with fans on opposite sides to dissipate heat. Another solution may have an underground coolant for geothermal cooling.
Another type of liquid cooling is immersive cooling, in which all the internal components are submerged in a non-conductive dielectric fluid and encased in a sealed container. Doing this helps transfer all the heat to coolant, which circulates to dissipate the heat.
Liquid cooling dissipates heat better than air. Hence, it can easily handle high computing densities, helping you perform computer-intensive applications. Moreover, it reduces energy consumption and uses less water, which lowers operating costs.
Air Cooling vs Liquid Cooling: Deciding Factors
To help to analyse these cooling systems, here is a tabular comparison of both.
| Aspect | Air Cooling | Liquid Cooling |
| Cooling Method | Provide air circulation through fans | Provides liquid circulation through water sprinklers or pipes |
| Performance | Suitable for medium workloads | Suitable for intensive workloads |
| Cooling Efficiency | Moderate | High |
| Energy Efficiency | Relatively less energy efficient when it comes to supporting intensive workloads | Highly energy efficient and can support a wide range of intensive tasks |
| Installation and maintenance | Less complex and easy to maintain. You can easily operate the equipment and swap components without dealing with complex procedures. However, there is water treatment and mechanical maintenance that you have to look after | It is a little complex and requires expertise. Often data centre teams with steep learning curves handle the cooling systems. In some cases, they may have to depend on the vendor for routine maintenance. |
| Heat Dissipation | It has a low capacity to dissipate heat | It has a high capacity to dissipate heat |
| Noise | It can produce moderate noise | Results in quiet operation |
| Price | Air cooling is less expensive than liquid cooling and thus offers higher performance for every amount you spend. However, with the increasing power requirements of servers, the air-cooling systems have to work hard to maintain operational temperature, resulting in high power consumption and costs. | Liquid cooling may incur high initial costs, but in the long run, it supports greater computing densities while reducing data centre footprint leading to space and cost savings. |
Ending Note:
Air and liquid cooling are employed highly in server racks in data centres. However, the choice between the two depends a lot on your computing requirements and budget and how you are willing to pay. Hopefully, the above information will help you make the right decision.