back to article Data centres gripped by power struggle

Data centre efficiency is a constant struggle. Choosing the right system for your required tasks is one challenge. Upgrade cycles cause power and heat issues. Existing techniques are continually refined. Combined with emerging technologies, optimal efficiency is a moving target. Space constraints are where the challenges of data …

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Got that right

A lot of our racks in the DC aren't even half full. The DC will only sell you so much power per rack*, and with the density of 1U servers you can stick in a rack, blowing your power budget is super easy.

The reason they will only sell you so much isn't because they are 'green' however, it's mainly to stay within their cooling window. Fully loaded racks mean more heat now than they did when the DC was designed.

* OK, thats not strictly true, but the cost for power goes up exponentially. I think we get 15A per rack, in some racks we've gone to 18A, which increases the price by almost half as much again. Going to 21A/24A, which is what we would need to run a full rack requires you to sell your first born.

Nice article Trev

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Re:Got that Right

As well as the power loading per rack you also need to consider if one half of a dual power feed goes down, and all the servers in that rack pull their juice off the remaining one. Get the sums wrong and the remaining feed overloads and trips out...

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Are Direct Current backbones making much headway?

I read about systems that wouldn't require transformation at each server being more efficient.

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DC backbones

But would require huge copper busbars to run across the data centre, in order to handle the high current. The cost of the copper - and the size of the busbars - outweighs the benefits of direct DC (48V) connections over 240Vac with local PSUs. A high performance PSU (or two for resilience...) per rack may make sense, though.

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48V

48V will, of course, require further inverters/regulators in the equipment to provide the end voltages necessary (3.3, 5, etc), which has an efficiency penalty. I don't see it being easy to make this more efficient than direct conversion from the mains, but obviously in certain cases it can be, or it wouldn't happen. (There is an inevitable extra inverter to provide the very low voltages and high currents for CPUs.)

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Click the link

Click the link to the Microsoft case study. They discuss DC versus AC supply and it's economic considerations. Apparently, MS engages in both...

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