Direct Liquid Cooling vs. Traditional Air Cooling in Servers

Direct liquid cooling (also known as Direct To Chip, or DTC) has several benefits compared to traditional air cooling which is more conventional, particularly in high density server environments. It has improved heat management which in turn translates to higher energy efficiency and quieter operations over time as well as lower operational expenditures. This cooling method also provides a wider range of benefits with respect to the environment which is consistent with sustainability objectives of many organizations today. 

In IT infrastructures, there is one cause that drives the rest, the need for cooling solutions, in this case server cooling which helps to achieve the best performance. With the increasing demand for more and more processing power and energy efficiency requirements, many businesses now face a dilemma – to go for direct liquid cooling solutions or conventional air cooling which ensures right temperatures for the servers to function effectively and reliably.

Read on to understand the two data center cooling technologies that are most used today in greater depth.

Understanding Cooling Methods

Traditional Air Cooling

For decades, traditional air cooling has been the go-to solution for managing temperatures in data centers. This approach uses large air conditioning units and fans to circulate cool air through server racks, which dissipates the heat created by the equipment. Typically, the cool air moves through raised floors or overhead ducts, helping servers maintain a safe, stable temperature.

How It Works:

• Air Conditioners (CRAC/CRAH units): These units cool the air and keep the data center at a steady temperature.
• Fans: Fans inside both the servers and the air conditioning units circulate cool air and help remove hot air generated by the servers.
• Ducts and Raised Floors: These channels distribute cool air evenly and help direct hot air out, keeping the data center’s temperature consistent.

Although traditional air cooling is popular because it's relatively straightforward to set up and has lower initial costs, it can struggle with energy efficiency, especially in high-density server setups.

Direct Liquid Cooling

Direct liquid cooling is a more advanced way to keep data centers cool, offering increased efficiency by circulating a liquid coolant directly to heat-generating components like CPUs and GPUs. The liquid absorbs heat, which it then releases at a heat exchanger before recirculating back into the system.

How It Works:

• Cold Plates: These are placed directly on the components and help move heat from the hardware into the coolant.
• Coolant Circulation System: Using pumps and pipes, this system circulates the coolant through the server racks and back to the heat exchanger.
• Coolant Distribution Modules (CDMs): These distribute the coolant to the cold plates and other cooling parts inside the server, regulating flow and temperature.
• Coolant Distribution Units (CDUs): CDUs keep coolant pressure within safe levels and send heated liquid to an external cooling system or heat exchanger.
• Heat Exchanger: This unit transfers the heat from the coolant to the outside environment, often using a secondary system like a dry cooler or chiller.

Direct liquid cooling is especially effective in high-density setups, where traditional air methods may not be enough to handle the heat. With its superior thermal efficiency, reduced energy use, and quieter operation, direct liquid cooling is an appealing choice for today’s data center.

The Pros and Cons of Each Cooling Method

Comparing the upsides and potential limitations of the two server cooling technologies also helps IT professionals understand the key differentiators between the two methods, as summarized below.  

Notable Benefits and Disadvantages of Traditional Air Cooling

Air cooling has traditionally been favored for its lower initial costs and, perhaps even more so, because of its ease of implementation. Nevertheless, these factors are increasingly less pronounced as liquid cooling technology evolves. This simplicity extends to maintenance; air-cooling systems are generally easier to service and require less specialized expertise compared to liquid cooling alternatives.

However, these advantages come with clear limitations. Air cooling systems are energy-intensive, particularly in high-density server environments where cooling demands are substantial. This not only drives up operational costs but also leads to a larger carbon footprint. Additionally, reliance on numerous fans and air conditioning units means higher noise levels, which can create a less comfortable working environment. Furthermore, as servers become more powerful, traditional air cooling may struggle to handle the heat output effectively, making it less suitable for modern, high-performance setups.

Direct Liquid Cooling (DLC): Advantages and Limitations

Direct liquid cooling offers a forward-thinking alternative, especially for data centers focused on energy efficiency and cost savings. By directly transferring heat from server components, DLC achieves superior thermal performance while significantly reducing the energy required for cooling. This translates to lower operational costs and a smaller carbon footprint—an increasingly important factor for businesses striving to meet sustainability goals.

Another key benefit of DLC is its quieter operation. Without the need for running fans at full speed , these systems operate with minimal noise, creating a more comfortable environment for on-site personnel. However, this innovation comes with higher initial costs. Installing DLC requires substantial investment in specialized equipment like pumps, cold plates, and heat exchangers. Maintenance is another consideration, as these systems demand specialized knowledge, potentially increasing ongoing expenses. However, with the cost of a data center related to the power delivered to the data center, the decision to use liquid cooling can reduce the construction costs of a new data center in many cases. 

DLC also enables more performance within a given power budget, a crucial advantage for high-density environments. Servers can operate at higher performance levels while maintaining optimal temperatures. This capability extends "boost" performance periods, where servers handle peak workloads more efficiently. It’s no surprise that DLC has become a go-to solution for high-performance computing setups.

That said, DLC has its challenges. Leaks, though rare in modern systems, can cause costly damage to sensitive components, necessitating careful planning and robust safeguards. Scalability can also be an issue. Expanding or modifying a DLC system to accommodate future growth often requires significant effort and expense. Still, for businesses looking to future-proof their data centers, the long-term benefits—especially in energy efficiency and sustainability—are hard to ignore.

Comparative Analysis: Direct Liquid Cooling vs. Traditional Air Cooling

Efficiency and Performance

When it comes to efficiency, direct liquid cooling outshines traditional air cooling. DLC systems efficiently dissipate heat directly from the source, keeping servers cooler and enabling higher performance without the risk of overheating. This is particularly vital in high-density environments, where heat can quickly build up and compromise performance.

Traditional air cooling, on the other hand, often struggles to maintain optimal temperatures in these settings. Hotspots can develop, reducing server reliability and performance. DLC’s ability to manage more heat per unit area makes it the superior choice for data centers with growing processing demands.

Cost-Effectiveness

The cost equation between air cooling and DLC is complex. Air cooling typically has lower initial costs because of its simpler infrastructure and easier installation process. However, the long-term expenses can add up due to high energy consumption and frequent maintenance needs for fans and air conditioning units.

In contrast, DLC requires a higher upfront investment to install specialized components. Yet, its energy efficiency and lower maintenance demands often result in significant cost savings over time. For businesses planning for the future, the potential for reduced operational costs may outweigh the initial expenses.

Environmental Impact

Cooling systems are an important factor in a business’s sustainability strategy. Traditional air cooling systems consume large amounts of energy and rely on resource-heavy air conditioning units, contributing to greenhouse gas emissions.

DLC, by comparison, is far more eco-friendly. Its lower energy consumption reduces carbon emissions, making it a greener choice for companies prioritizing environmental responsibility. Additionally, its improved efficiency can help businesses comply with increasingly stringent environmental regulations.

Scalability and Future-Proofing

Scalability is a crucial consideration when choosing a cooling system. Air cooling is relatively easy to scale by adding more air conditioning units or fans. However, as server densities increase, its effectiveness diminishes, and the costs of scaling can become prohibitive.

DLC offers a more forward-looking solution. Although it’s more complex to implement, it handles high thermal loads efficiently without requiring a significant increase in energy use. This adaptability makes DLC a strong choice for data centers anticipating growth and technological advancements.

Conclusion

Switching from traditional air cooling to direct liquid cooling offers clear advantages for modern data centers. Enhanced energy efficiency, reduced operational costs, and a smaller carbon footprint are just a few of the benefits. DLC is particularly valuable in high-density environments, where its superior heat management and quieter operation stand out.

While the initial costs can be daunting, the long-term savings and environmental benefits make DLC a compelling option for businesses aiming to future-proof their infrastructure. With ongoing advancements in liquid cooling technology, it’s poised to become an even more attractive choice for data centers striving to meet growing demands for performance and efficiency.

To learn more, visit: Supermicro Rack-Scale Liquid Cooling Solutions

Additional Resources:

• Direct Liquid Cooling: A Game Changer for Data Center Power | White Paper
• Supermicro Liquid Cooling Solutions | Datasheet
• Total Rack Scale Liquid Cooling Solutions | Brochure