Aging servers are big energy consumers in the data center

“The most wasteful energy consumers in data centers (especially in low-PUE data centers) are inefficient servers” according to Winston Saunders. He placed a very interesting blog on  “The Server Room Blog” of Intel.

As showed in the figure this data center case shows that in this particular data center servers older than 2007 consume 60% of the energy, but contribute only an estimated 4% of the compute capability.

William Carter, Elephant in Data Center

Based on this issue and the fact that servers efficiency closely followed Moore’s law he propose a new data center metric, the Server Usage Effectiveness or SUE metric.


With an age of 0 years SUE sets Today = 1.0. With an age of 3 years SUE sets 2.8, which implies that you have approximately 2.8 times the number of servers you actually need (based on current data center productivity and workload).

The blog goes even one step further by combining SUE with PUE and defining the Total data center Usage Effectiveness,


This is a very interesting pragmatic approach to improve the energy consumption and energy efficiency of the data center. The power supply to the IT infrastructure (servers, storage and network) in a data center is not very effective. There is a tremendous loss in this energy supply chain (starting from power station, on to power grid, UPS, PDU, …) so that finally only a couple of percent of the original energy (power plant) is actual used for data processing. The only way to get quick results is to start on the demand side. This part of the infrastructure (IT equipment) is relatively easy to the change (months instead of years for components upstream in this energy supply chain). And last but not least a small result and the end of the chain gives a huge result upstream.

Just as for the PUE a first-order approximation is just right to find the “low hanging fruit”. I was even wondering if you could simplify things by just using the average age of servers instead of making cohort statistics as showed in the blog.

As for  power consumption of servers versus other IT equipment (storage and network devices). In the EPA Report to Congress on Server and Data Center Energy Efficiency it is suggested that, servers will on average account for about 75 percent of total IT equipment energy use, storage devices will account for around 15 percent, and network equipment will account for around 10 percent.

I’m very interested in the follow up of the blog entry of Saunders.

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