AC/DC – 80s Rock Band or Data Center Power Distribution Terminology?

Good question but since you’re reading this on Dell’s CIO-focused blog and not Creem, you should assume it is the latter. This is a topic that's been widely discussed across our industry, including this article from Jeff Burt of eWeek.

Grid designs for data center power grid infrastructures need to include careful consideration of uptime and efficiency. Current flow needs to be steady and always available. It should also be cost-effective and “green.”  The most fundamental consideration to be made when planning a new data center is whether to provision it with AC or DC power.  The majority of IT data centers today use  AC power throughout. This is not surprising, given the prevalence of AC power grid infrastructure in centers of global commerce.  A century of AC power grid refinements (i.e. transformers, circuit breakers, fuses, standards) have resulted in a generally accepted view of AC power as dependable. Couple that with these limitations imposed by the perception of DC power grid selection (distances of less than one mile and fewer available hardware choices) and you might conclude that DC power type data centers are rare. This is not true.

There remain a large number of DC powered data centers throughout the world, and new ones continue to be built, driven by telecommunication service expansion across emerging regions. DC power holds advantages for telecommunication networks that relate to always-on “dial tone” service level requirements. Network data flow for audio streaming is circuit-based, rather than packet-based. Slight disruption in sequential read/writes results in a poor user experience. Until recently, 1993 to be exact, AC power was susceptible to a bad thing called “current harmonics,” which can result in overheated neutral circuits and transformers. 

For these reasons, telecommunication companies embraced DC power early in their history of operations. DC power continues to be preferred for telecom networks due to the massive install base already in use, and DC power’s success in delivering incredible “dial tone” service levels — “If it ain’t broke, don’t fix it,” you might say.

Some other verticals for which DC power is attractive include:  remote and mobile computing (oil rigs, ships, jets), military, and video-content providers. The debate goes on, about the virtues of AC vs. DC power and while the efficiency rating between the two standards has come close to parity over the years, Dell remains a strong advocate of choice in the OEM market. This is why we have chosen to partner with NEI to introduce the NEI E2710, a DC-powered server that meshes with Dell’s DMC systems management console and packs the same performance punch that Dell’s Nehalem-based PowerEdge servers do.

The past few years have seen dramatic enhancements in the efficiency of IT equipment, which has resulted in impressive efficiency gains for AC power equipped servers and storage.  Power supplies now run at 80 percent and higher efficiency levels.  Airflow and cooling design considerations have pushed out bulky component cables, in favor of skinny ones.  Heat dissipation from components inside a  chassis is now carefully considered when product design teams develop new platforms.  Airflow is paramount, low “drag coefficients” enable fans to cool heat producing components with ease.  The fans themselves have been completely redesigned, and are more power efficient themselves.  In some large scale processor intense deployment, servers are “running naked” sans chassis, further eliminating drag coefficients while nestled inside their 19 inch-wide, 42U high racks.  As a result, the power efficiency possible in today’s AC powered data center environments is excellent.  This is fantastic news, both for companies with AC powered data centers and for everyone. 

Now, you have a DC powered server that takes advantage of all of these recent enhancements, and delivers Dell dependability and power.  Use it wisely.

About the Author: David Havener