The old adage ‘you can’t improve what you can’t measure’ seems particularly apt when it comes to bringing data centres up to a point where their power consumption, and corresponding carbon emissions, can be properly reported back to the business.
Frost & Sullivan ICT practice research director, Arun Chandrasekaran, says that, in light of the impending carbon tax, it is essential for data centre owners, operators and enterprises to begin by actually measuring the power usage effectiveness (PUE) of their facilities.
In theory, all the power that goes into a data centre should go into the IT equipment located there, but in the real world, power distribution losses and energy siphoned off for use in cooling and lighting. This means that understanding PUE — the total facility power divided by IT equipment power — is the first stop in understanding data centre energy use.
“The ideal value for PUE should be one because all of the facility power in a real world scenario, or rather in an idealistic situation, should go towards IT power — but it doesn’t,” Chandrasekaran says. “At the end of the day, if you don’t even know what value it is, if you’re not even measuring it right, how can you improve on it?”
For Canberra Data Centres managing director, Greg Boorer, getting a grip on energy consumption means measuring power usage at multiple points across the facility; that is, multiple points along the “electrical consumption pathway”.
“What you’re trying to break down is how much energy actually gets to the IT equipment, how much energy then goes into the facilities, so that’s cooling, lighting, supporting infrastructure but not IT equipment,” he says.
“If you have multiple points of measurement — at different sub-distribution boards, at different sides of the UPSes (uninterruptible power supplies), at the power distribution level within each rack — you can actually determine where pockets of inefficiencies lie within your own facility, then you can take measures to remove or remediate any sort of inefficiencies.
“[But] the big challenge with all reporting now is separating IT electrical consumption from electrical consumption associated with things like your cooling, chillers, lighting, security systems and the like.”
Greening your data centre
It is no secret that cooling takes the lion’s share of power consumption in a data centre. According to Oracle master principal systems architect, Mike Coleman, as much as 60 per cent of the power to a data centre goes into cooling, rather than running, IT equipment. Hence, it is imperative for data centre operators to lower the amount of energy used in keeping kit cool.
The main issue, Coleman says, is underfloor cooling; a practice considered outdated but widely used in ‘traditional’ data centres. With underfloor cooling, cool air is pumped under the floor and drawn up to cool the equipment then expelled back into the room. What this does is mix hot air ported from IT equipment with the cool air from conditioning units making for a pretty inefficient system.
To add to this, the energy consumption — and corresponding heat output — of modern equipment racks has dramatically increased in recent years. Where underfloor cooling could cope with the equipment using around of five kilowatts per rack, today’s densities have increased as much as eightfold.
“Today’s equipment can be up to 30 to 40 kilo watts per rack, so you can’t cool that with underfloor cooling,” Coleman says. “The idea is to take the cooling to the source and what that actually means is the equipment in the rack that’s generating the heat needs to be cooled directly.”