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How to Define a High-Density Server Rack

By: Tom Banta on February 25, 2019

Density is a term that gets thrown around quite a bit when it comes to data center computing. Many data centers market themselves as “high-density” facilities, but they don’t always do a very good job of explaining what that means. The implication is that high-density facilities offer improved performance, computing power, and more efficient energy consumption.

Generally speaking, density is a power consumption measurement that calculates the average amount of power needed per rack. Data centers used to gauge a building’s power density in terms of watts per square footage (W per square foot), but with the miniaturization of processors and computing equipment, this formula no longer accurately reflects a facility’s true performance.

What Is Considered a High-Density Rack?

Whereas a typical server rack usually required about 3-5kW in the past, the average rack density today is about 7kW. Since servers have become more powerful over the years, it’s not uncommon for a standard rack to have a density as high as 10kW. Most data centers fall somewhere within the 1-10kW range.

Anything over 10kW qualifies as a high-density rack (although this threshold is steadily rising). Racks ranging from 16kW up to 20kW are becoming much more common, with specialized data centers handling more intensive computing workloads deploying cabinets with densities as high as 25 to 40kW.

What higher rack density really means in practice is that each server in the rack is powerful enough to handle heavier workloads and computing tasks. The increased power demands are a byproduct of better performance and capacity. As engineering trends continue to reduce the size of computing equipment, it becomes easier to fit more servers into a rack, which further increases the overall power density.

What’s Driving the Move to Higher-Densities?

While improved server technology is responsible for some of the shift to high-density deployments, the real driving force is AI and machine learning. Many of today’s businesses rely on sophisticated analytics to generate business insights from the massive amount of unstructured data they gather over time. These programs are incredibly powerful, but they also require a huge amount of raw computing power.

Cloud computing and the data center trends toward virtualization have also contributed to the rise of high-density server racks. More and more companies are turning to these services for computing power “on demand,” and all that processing capacity has to come from somewhere. By implementing high-density rack deployments, data centers can meet those needs efficiently while still retaining the room and flexibility to grow in the future.

Benefits of High-Density Racks

By increasing rack density, data centers can pack more computing power into a smaller space. This means reduced costs in terms of physical infrastructure because the data center can now be located in a smaller space, reducing fixed overhead costs. Spreading several low-density servers over a large area leads to much higher data center cooling costs and also forces applications to be distributed over multiple servers and cabinets.

Having fewer server racks also makes it easier to manage computing infrastructure. While the powerful blade servers that are typically used in high-density deployments are more expensive than traditional servers, they provide more flexibility and better value over time.

Drawbacks of High-Density Racks

Since high-density racks draw more power, that means they require more cooling. At a certain point, traditional air cooling solutions become less viable. Anything over 25kW per rack calls for more innovative data center cooling technologies to be deployed efficiently. Many data centers have already implemented various forms of liquid cooling and cold aisle containment solutions to address the heat problems that high-density servers present.

The additional power and cooling demands also make high-density racks themselves heavier and more expensive. A traditional server rack, which integrates power distribution and other connectivity infrastructure, can weigh as much as 2,000 lbs. A high-density rack, however, can weigh 3,500 lbs and more. The servers used in a high-density deployment often cannot be distributed throughout a facility, which can sometimes limit flexibility if the data center has not made a commitment to high-density performance.

High-density server racks have become a fixture of today’s data center infrastructure. As processor and storage technology continues to pack more power into smaller components, densities will likely to continue to trend upward. By partnering with data center facilities committed to high-density deployments, companies can put themselves in the best position to compete in the future.

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