Evaluate air cooling vs. liquid cooling for your data center

Pros and cons of air cooling

Most data centers adopt air cooling as their first cooling method. The technology has become more efficient over time, but the basic setup has remained the same: An HVAC system removes warm air and generates cold air that circulates around hardware in the facility. Air cooling generally uses one of three setups -- room-, row- or rack-based cooling -- depending on what a facility requires.

Because air cooling is so widely used and understood, most data center staff know exactly how to maintain and support it. Maintenance activities are straightforward and skills can transfer across facilities. Facilities have many vendor options for air cooling, which enables them to optimize cooling expenses.

Physical and virtual densities increase as systems use more storage and rack space, which can make it a challenge for HVAC systems to keep everything cool. This leads to increased operating expenses -- and with energy costs on the rise, air cooling can easily become too expensive for organizations to justify. Additionally, data centers that use evaporative cooling or cooling towers as part of their air cooling systems might face water restrictions and shortages due to climate change.

Another challenge air cooling presents is the noise pollution created by an increased number of cooling fans and pumps. Fans and pumps produce a lot of noise, which poses hearing risks for data center staff working in the facility.

Why liquid cooling works

Liquid cooling can conduct heat more efficiently than air, which means it can handle higher-density facilities. There are three main options for liquid cooling: direct-to-plate cooling, rack/server cooling and immersion cooling. They all work by pumping cold liquid close to or directly over hardware to carry out the heat exchange. The liquid constantly circulates, removing heat almost as quickly as it's generated.

Many organizations switch from air to liquid cooling because liquid cooling significantly reduces energy consumption and uses less water than many air cooling systems, which leads to lower operating costs. It also takes up less space, produces less noise and makes for an overall cooler working environment for IT staff.

Challenges of liquid cooling

Most IT and data center administrators require specialized training to work with liquid cooling systems. This can lead to higher costs, as an organization must bring in new employees or consultants. Data centers must also adopt new management practices and frameworks to help staff, which means creating new processes, procedures and SLAs.

Immersion cooling requires staff to don protective equipment and save expensive cooling liquid to change or upgrade hardware. Depending on how often a data center's hardware must be handled and the type of cooling liquid it uses, such processes could present hazards to staff.

Relatively few vendors offer liquid cooling, and these vendors typically only install them on their own hardware. An organization might not currently be able to mix and match hardware with liquid cooling, making data centers susceptible to single vendor lock-in. Depending on the age of hardware, a data center also simply might not be able to retrofit it for liquid cooling.

Air-assisted liquid cooling, a hybrid liquid cooling system, uses separate enclosures that surround the hot hardware and don't attach directly. However, such a system requires support staff to understand both types of cooling technology and how to manage and support them.

When should a data center switch from air to liquid cooling?

Liquid cooling is still a new technology, which means it's likely to evolve rapidly in the coming years. However, if a data center relies on high computing power and high-density storage, an organization might consider exploring its liquid cooling options sooner rather than later. Facilities that can still manage cooling with air and don't face any significant hardware upgrades or other cost hikes can continue using air cooling.

Both cooling options make sense for different data center situations. For many data centers, it currently makes the most sense to stay updated on liquid cooling and start laying the foundation for it, but to stick with air cooling for now.