Once you tick off the low-hanging fruit of efficient kit, tidiness, virtualisation and setting a realistic temperature, it's time to think about airflow.
Servers and other appliances generally push hot air out their rears, so it is important to make sure that hot air doesn't travel in the direction of something you want to keep cool. The most common response to this issue is to run a “hot aisle/cold aisle” regime whereby you make sure hot air travels in one direction only. That means placing racks so that their rears face one another, with the result being a nastily-warm aisle between the two.
Such an arrangement means all the hot air ends up in once place from which it can be whisked away and treated, rather than spreading warm air around.
“You are not optimising cooling if you mix hot and cold air,” says Emerson's Grandjean-Thomsen.
If your data centre or server room isn't set up in this way, the bad news is that you'll almost certainly need to stop operations in order to re-rack kit in a more cooling-friendly way. If that's not an option, the likes of Schneider IT offer hot aisle containment systems, drop-in pods that isolate hot aisles and bring cooling to where it can be most impactful.
Beyond these tactics like a raft of techniques that fall under the label of 'data center infrastructure management'. Best-suited to larger data centres, because of their reliance on fine monitoring of a facility, DCIM requires a dedicated application (which means an additional server to power and cool) but can return inform power management and cooling practices that operate at a very granular level. For example, DCIM makes it possible to identify servers that consistently run hot because they are being worked hard, or even look at which sockets are sucking most energy. With that knowledge in hand, you can then distribute workloads among different boxen to prevent hot spots from forming.
It's also possible to fight back against power bills by making them someone else's problem . Electricity procurement is, according to Schneider IT's Tyrer, a fiendishly tricky business. Schneider's Australian arm therefore acquired a specialist consultancy to crunch the numbers offered by electricity companies and will happily offer you its services. Perhaps if your CIO asks you about PUE, pointing him or her in the direction of such a consultancy wherever you reside will deflect the matter and demonstrate your own efficiency at the same time. &ref;
Re: PUE can be less than 1
PUE less than 1?
Why, you could sell power back to the grid!!
The term PUE I'm afraid is thrown about with the Uptime scam / cartel's tier ratings, that is, handy to talk to CEO's and PHB's over golf, but actually useless unless the measurements are quantified.
PUE can be less than 1
There's plenty of room to improve PUE more. Iceotope, a new technology company based in Sheffield, is offering liquid cooled kit which means that the heat is extracted without active cooling and, as you get to drop the fans from each blade, the PUE is (at least in one interpretation of that number) ends up being less than 1.