With constant streams of data emerging from the Internet of Things, video, artificial intelligence and more, it’s no surprise we are expected to generate 463 exabytes of data each day by 2025.

How we access and interact with data is constantly changing and is going to have a real impact on the processing and storage of that data. In just a few years, it’s predicted that global data storage will exceed 200 zettabytes with half of that stored in the cloud.

This presents a unique challenge for hyperscale data centres and their storage infrastructure. According to Seagate, cloud data centres choose mass capacity hard disk drives (HDDs) to store 90% of their exabytes. HDDs are tried and tested technology typically found in a 3.5-inch form factor. They continue to offer data centre operators cost-effective storage at scale. The current top-of-the-range HDD features 20 TB capacity. By the end of the decade, that is expected to reach 120+ TB all within the existing 3.5-inch form factor.

The practical implications of this show a need for improved thermal cooling solutions. More data storage means more spinning of the disks, higher-speed motors, more actuators – all of which translates to more power being used. As disks go up in power, so does the amount of heat produced by them. Next, with the introduction of helium into the hard drives in the last decade, performance has not only improved thanks to less drag on the disks, but the units are now sealed.

There is also ESG compliance to consider. With data centres consuming 1% of global electricity demand, and cooling power accounting for more than 35% of a data centre’s total energy consumption, pressure is on data centre owners to reduce this consumption.

Comparison of cooling technologies

Traditionally, data centre environments use air-cooling technology. The primary way of removing heat with air-cooling methods is by pulling increasing volumes of airflow through the chassis of the equipment. Typically, there is a hot aisle behind the racks and a cold aisle configuration in front of the racks which dissipates the heat by exchanging warm air with cooler air. Air cooling is widely deployed and well understood. It is also well engrained into nearly every data centre around the world. However, as the volume of data evolves, it is becoming increasingly likely air cooling will no longer be able to ensure an appropriate operating environment for energy dense IT equipment.

Technologies like liquid cooling are proving to be a much more efficient way to remove heat from IT equipment. Precision liquid cooling, for example, circulates small volumes of dielectric fluid across the surface of the server removing almost 100% of the heat generated by the electronic components. There are no performance-throttling hotspots and no front-to-back air-cooling, or bottom to top immersion constraints which are present in tank solutions. While initial applications of precision liquid cooling have been in a sealed chassis for cooling server components, given the increased power demands of HDD, storage devices are also an ideal application.

High-density storage demands

With high-density HDD, traditional air-cooling pulls air through the system from front to back. What typically occurs in this environment is that disks in the front become much cooler than those in the back. As the cold air comes and travels through the JBOD device, the air gets hotter. This can result in a 20°C or more temperature differential between the discs at the front and back of the unit depending on the capacity of the hard drive.

For any data centre operator, consistency is key. When disks are varying by nearly 20°C from front to back there is inconsistent wear and tear on the drives leading to unpredictable failure. The same goes for variance across the height of the rack as lower devices tend to consume the cooler air flow coming up from the floor tiles.

Liquid cooling for storage

While there will always be variances and different tolerances taking place within any data centre environment, liquid cooling can mitigate for these variances and improve consistency. In 2022, Meta published a study showcasing how an air-cooled, high-density storage system was re-engineered to utilise single phase liquid cooling. The study found that precision liquid cooling was a more efficient means of cooling the HDD racks with the following results:

• The variance in temperature of all HDDs was just 3°C, regardless of location inside the JBODs
• HDD systems could operate reliably in rack water inlet temperatures up to 40°C.
• System-level cooling power was less than five percent of the total power consumption.
• Mitigation of acoustic vibrational issues.
  

While consistency is a key benefit, cooling all disks at a higher water temperature is important too. This means data centre operators do not need to provide chilled water to the unit. Reduced resource consumption – electrical, water, space, audible noise, etc. – all lead to greater reduction in TCO and improved ESG compliance. Both of which are key benefits for today’s data centre operators.

As demand for data storage continues to escalate, so will the solutions needed by hyperscale data centre providers to efficiently cool the equipment. Liquid cooling for high-density storage is proving to be a viable alternative as it cools the drives at a more consistent temperature, and removes vibration from fans, with lower overall end-to-end power consumption and improved ESG compliance. At a time when data centre operators are under increasing pressure to reduce energy consumption and improve sustainability metrics, this technology may not only be good for the planet, but also good for business.

Enabling innovation in storage systems

Today’s HDDs are designed with forced air cooling in mind, so it stands to reason that air cooling will continue to play a role in the short term. For storage manufacturers to embrace new alternative demonstrations of liquid cooling technology like the one Meta conducted is key to ensuring adoption. Looking at technology trends moving forward, constantly increasing fan power on a rack will not be a long-term sustainable solution.

Data halls are not getting any larger and costs to cool a rack are increasing. The need for more data storage capacity at greater density is exponentially growing. Storage designed for precision liquid cooling will be smaller, use fewer precious materials and components, perform faster, and fail less often. The ability to deliver a more cost-effective HDD storage solution in the same cubic footprint delivers not only a TCO benefit but contributes to greater ESG value as well.

Making today’s technology more efficient and removing limiting factors for new and game changing data storage methods can help us meet the global challenges we face and is a step forward towards enabling a better future.