Rack Density is Rising (Andy Lawrence)

Overview

This article, by Andy Lawrence, was published in the Uptime Institute Journal in 2020 and is freely available. It summarises Uptime's 2020 survey data on rack power density. Its main message is that average density is climbing steadily, but the long-forecast industry-wide shift to 20 kW racks has not happened. The most compute-intensive loads sit in a small group of hyperscale, HPC and specialist sites. The article distinguishes highest, mean and modal (most common) rack density as planning metrics.

According to the findings, most respondents reported their highest-density racks in the 10-19 kW range year over year. In 2020, 71% reported a modal server rack density below 10 kW, and only 16% widely deployed 20 kW or more. Mean density was calculated after excluding respondents above 30 kW as high-performance outliers. This distinction shows that looking only at the average can mislead facility planning.

About half of organizations said their average density was increasing. Virtualization, containers and slowing Moore's law push utilization and per-rack power upward. The article rests on 2020 data; the effect of AI loads in later years is outside its scope. These trends suggest that the average rises slowly while extremes can climb much faster. Cooling and power distribution should therefore be sized for the cluster formed by the densest racks in the facility, not only for the average; otherwise a design based on the average may not carry a high-density cluster.

Key points

1. Most respondents reported their highest-density racks in the 10-19 kW range year over year.
2. In 2020, 71% reported a modal server rack density below 10 kW; only 16% widely deployed 20 kW or more.
3. Mean density was calculated after excluding respondents above 30 kW as outliers.
4. About half of organizations said their average density was increasing.
5. Virtualization, containers and slowing Moore's law push utilization and per-rack power upward.
6. The general shift to 20 kW racks has not happened; dense loads sit in a few hyperscale, HPC and specialist sites.
7. Highest, mean and modal rack density are distinct planning metrics.

Using it in design

• Ask users for modal and peak rack density separately, not just the average, and size cooling and power for the peak cluster.
• Use the 2020 baseline (modal below 10 kW) as a sanity check when a legacy enterprise template is selected.
• Do not treat average density alone as sufficient for planning.

Who should read it

Design engineers and capacity planners sizing power and cooling by rack density.

Publication details

Authors

Andy Lawrence

Publisher

Uptime Institute Journal

Year

2020

Document language

English

Source type

Industry body

Access

Free to read

Licence

Copyright retained; citation only — the publisher’s terms apply to the original document

Citation