<div dir="ltr"><div dir="ltr">On Wed, Dec 18, 2019 at 10:48 AM Thomas Bellman <<a href="mailto:bellman@nsc.liu.se">bellman@nsc.liu.se</a>> wrote:<br></div><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 2019-12-18 15:57, Rod Beck wrote:<br>
<br>
> This led me to wonder what is the inefficiency of these servers in data> centers. Every time I am in a data center I am impressed by how much> heat comes off these semiconductor chips. Looks to me may be 60% of the> electricity ends up as heat.<br>
What are you expecting the remaining 40% of the electricity ends up as?<br><br>
There is another efficiency number that many datacenters look at, which<br>
is PUE, Power Usage Effectiveness. That is a measure of the total energy<br>
used by the DC compared to the energy used for "IT load". The differece<br>
being in cooling/ventilation, UPS:es, lighting, and similar stuff.<br>
However, there are several deficiencies with this metric, for example:<br>
<br>
- IT load is just watts (or joules) pushed into your servers, and does<br>
not account for if you are using old, inefficient Cray 1 machines or<br>
modern AMD EPYC / Intel Skylake PCs.<br>
<br>
- Replace fans in servers with larger, more efficient fans in the rack<br>
doors, and the IT load decreases while the DC "losses" increase,<br>
leading to higher (worse) PUE, even though you might have lowered your<br>
total energy usage.<br>
<br>
- Get your cooling water as district cooling instead of running your own<br>
chillers, and you are no longer using electricity for the chillers,<br>
improving your PUE. There are still chillers run, using energy, but<br>
that energy does not show up on your DC's electricity bill...<br>
<br>
This doesn't mean that the PUE value is *entirely* worthless. It did<br>
help in putting efficiency into focus. There used to be datacenters<br>
that had PUE numbers close to, or even over, 2.0, due to having horribly<br>
inefficient cooling systems, UPS:es and so on. But once you get down<br>
to the 1.2-1.3 range or below, you really need to look at the details<br>
of *how* the DC achieved the PUE number; a single number doesn't capture<br>
the nuances.<br></blockquote><div><br></div><div>Google has some information on PUE at <a href="https://www.google.com/about/datacenters/efficiency/">https://www.google.com/about/datacenters/efficiency/</a> -- the tl;dr is that we have a datacenter PUE of 1.06, and a campus (including power substation) PUE of 1.11. By comparison, most large datacenters average around 1.67.</div><div><br></div><div>Damian</div></div></div>