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» VIEW ALL POSTS Jun 8 2009   8:46PM GMT

Energy Star for servers: Unexpected impact on data center efficiency

Posted by: Jbeltran
Data center power
Energy Star
Green data center

This blog post was written by contributer Julius Neudorfer.

It’s out! After several years, the Environmental Protection Agency (EPA) has released the first version of the Energy Star specification for servers. Now, how fast can we adapt?

It was created through a solid collaborative effort between government and major equipment vendors. The spec addresses many areas of power usage and waste in the power supply (and redundant power supplies) for servers. Until now, there has been no standard for server power supply efficiency — the existing Energy Star program covered PCs but exempted servers. Most server manufactures have been voluntarily improving their power supply and server energy efficiency, but few published their complete specifications. The spec also addressed standby power and efficiency at less than full load. In fact, it calls for a minimum of 85% efficiency at 50% of rated load, and 82% at only 20% of rated maximum. This is an extremely important step forward, since many servers normally run with dual power supplies, each one only loaded at 20-30% of its maximum rating due to load sharing (under 2N, they normally never operate above 50%). The spec also calls for the second (redundant) power supply to have a static loss of 20 W or less. This is a major improvement to the fixed losses found in typical servers with dual power supplies.

The spec covers more than just power supplies. It even limits the idle power of hard drives to 8 W and memory to only 2 W per gigabyte. (Note: There are some limitations on this, but is part of the requirements.)

Power management is required! Moreover, the spec mandates that idle servers must draw much less power than existing servers and that power management must be enabled when shipped. Until now, most manufacturers shipped servers with the power management disabled, and most IT shops never used or chose not to enable it. In fact, the Energy Star spec calls for a base server with one CPU to draw only 55 W at idle. This is about one-third or less of the typical single CPU server, which can draw 150-200 W at idle.

However, the spec excludes blade servers! Due to the complexity of blade chassis, power supply options and server blades from different vendors, this first standard wisely decided not to further delay the release date to include blade servers. (This is still being worked on and is expected to be addressed later this year.)

I predict the specification will have unexpected effects on data center efficiency in the future. While at first blush all this should save energy in the data center, this is just the first of many mandated server and IT equipment energy-efficiency regulations that will impact the relatively flat power curve of data centers. Until recently, most servers and IT equipment drew a substantial amount of the maximum power, even while idle. As these new servers begin to replace older equipment, it will begin to be felt and seen in the IT power load, which will vary much more widely that it does today. This means the UPS and cooling loads will become much more dynamic and will require more responsive, scalable infrastructure systems to operate efficiently (on demand) at peak power and cooling loads as well as low loads.

The data center infrastructure of the future will need to be responsive to continuous and rapid changes in power demands and especially to moving and changing cooling loads, as IT equipment powers up and down in different areas of the floor. As this new paradigm evolves, The “smart” data center of the future will use advanced power management systems to interactively broker and negotiate power requests (and perhaps charges and rates) from IT equipment to the UPS, intelligent PDUs and, most importantly, intelligent cooling systems, which will need to adapt to varying heat loads while trying to operating efficiently.

Stay tuned as this specification develops. As they say in the auto business, “Your actual mileage may vary”

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