Microsoft Eliminates Server Fans, Despite PUE Hit

SeanM

Posted January 31st, 2011

PWM is described as “pulse with modulation” as opposed to the proper description “Pulse Width Modulation”. Assuming it’s not a simple typo, it’s important to describe the concept: you can say that the fan is fed power for a certain percentage of a second per second (or a certain percentage of a millisecond per millisecond, etc), so it’s pulsed on and off quickly. The longer the ‘on’ period, the more air the fan moves with the fan ‘coasting’ back down between pulses. It’s how you get a gradual increase in effective speed when using a device that only has 2 states: on and off.

As an analogy, imagine if your car’s engine could only run at one speed, and to change the effective speed to less than full speed the drive wheels were taken off the ground for, say, 1/2 of every second (with the engine capable of running the entire time, but not needing to whenever the wheels are off the ground): you’d get a drive forward each time they were on the ground, and a coast when they were off. If you reduced the amount of time they were on the ground to 1/4 of a second, you’d get less energy pushing the the car forward effectively and a lower average speed, and if you increased it to 3/4 of the time, you’d get more. To get ‘max speed’ you’d just keep the wheels on the ground and engine running the whole time, and to stop you’d just leave them off the gorund and the engine off.

[...] just been reading a piece about Microsoft removing fans from their data center servers and that having a negative effect on their PU…. I’ve written on this blog before about the problems with PUE, now we have proof that it [...]

[...] Mr. Heiliger also said that by getting rid of air-conditioning systems that cool most data centers, the Prineville one had drastically reduced a important measure of efficiency, known as power usage effectiveness. While the average data center has a P.U.E. of 1.5, the Prineville facility has a P.U.E. of 1.07. Google, Microsoft and other large data center operators have also claimed P.U.E. ratios that are significantly lower than industry averages. [...]

[...] Mr. Heiliger also pronounced that by removing absolved of air-conditioning systems that cold many information centers, a Prineville one had drastically reduced a critical magnitude of efficiency, famous as appetite use effectiveness. While a normal information core has a P.U.E. of 1.5, a Prineville trickery has a P.U.E. of 1.07. Google, Microsoft and other vast information core operators have also claimed P.U.E. ratios that are significantly lower than attention averages. [...]

Nash N

Posted June 18th, 2011

Good article. I’d point out, however, that the savings, and hence effect on PUE, was, by Microsoft’s own admission, rather small. PUE is really meant to look at big changes in efficiency. According to this article http://blogs.carouselindustries.com/green-it/what-is-pue-power-usage-effectiveness/ the average data center achieves a rating of 1.8 but Google is already hitting an astonishing 1.1.