BT recently embarked on an overhaul of its datacentre infrastructure as part of its efforts to shave an estimated £400m off its annual electricity bill and cut carbon emissions by 80 per cent.

Although the programme is still at its early stages, it has already forced the company to address what it believes are a number of myths concerning how datacentres are built and run.

Steve O’Donnell is BT’s head of datacentres and customer experience. He said datacentres have traditionally been built to use AC power sources and recycled air that maintains a steady temperature of 20-24C because using external air for cooling would create too much condensation.

“The idea that datacentres need to run at temperatures of 20-24C is madness, while the assumption that computers are sensitive to humidity is not true either,” he said. “Most vendors supply equipment that will run at up to 50C, which takes about 85 per cent off our cooling costs. We do not want to buy stuff that cannot run hot, and we need to make it a commercial imperative for [hardware] vendors to consider energy efficiency.”

BT is also piping fresh air into its datacentres to provide cooling. This is something that other companies have shirked from in the past because of worries about contamination and condensation.

“The air inside might be 10C hotter, so why would you want to use that ­ it makes no sense,” argued O’Donnell. “Condensation does not cause failures and only refrigerated cold surfaces cause condensation ­ if you have no cold surfaces you do not have condensation. The cost of humidifiers is huge but the cost of blowers to blow in fresh air is a lot less ­ around £2,400 against £11,200 ­ and the capital costs are much lower as well.”

Ovum analyst Graham Titterington agreed that fresh air cooling has its advantages, but argued that running equipment at up to 50C is risky. “If you go beyond the equipment’s temperature limits, it can badly malfunction and data can become corrupted, but BT is presumably being careful about which kit it is exposing to higher temperatures.

Generally speaking, the higher performance it is, the hotter it can run,” he said.
The concept of using a DC rather than an AC power source in datacentres is not new, and converting existing sites to use DC power is uneconomical in the majority of cases. But BT maintains that adding DC-enabled equipment to its facilities has yielded significant savings.

“Some people say you can only buy equipment that uses AC power, but that is not true - you can buy computers and network equipment that uses DC power. It is marginally more expensive but the TCO [total cost of ownership] and ROI [return on investment] is much better. In many cases, the payback is months rather than years,” said O’Donnell.

As well as being more reliable ­ meantime between failure (MTBF) for DC equipment is calculated at thousands of years ­ O’Donnell estimates that the 250 sites BT has upgraded to using DC power use only 40 per cent of the power they did with AC.

Simon Pamplin, systems engineering manager for the UK and Ireland at SAN switch specialist Brocade, said manufacturers are not keen to build DC equipment for western datacentres, which are still largely structured for AC power sources. “It is something we are thinking about but there is not enough demand [for DC equipment] in the UK or the US yet ­ it comes mostly from the Far East,” he said.

BT said it has successfully decommissioned more than 4,000 servers in the past six months, and this has also made a massive difference to costs. “We are constantly migrating legacy equipment onto lower cost, lower energy computers - keeping data online all the time when it is not necessary is a waste of money and energy,” O’Donnell said. “The best approach is to delete data, while the second-best is to put it on tape or disks that do not spin when they are not used.”

This approach is not always as simple as it sounds, however. Discovering and evaluating all the data that an organisation has on its servers is no mean feat, but this has to be done before the decision to delete it or migrate it to cheaper storage medium can be taken.

“There are certain file types that are not going to be needed, and you can move according to their date, but the big problem that everybody has is that they do not know what it is they are moving,” said Peter Williams, communications manager and senior analyst with research company Bloor.

Expert comment: BT’s approach will not suit all firms
Gartner analyst Rakesh Kumar believes BT is on the right track but points out that its datacentre requirements are far from typical.

"I would agree that there is little DC-enabled equipment out on the market right now. I do not dispute what BT says, but it has to be remembered that a lot of specific telecommunications equipment runs on DC power, and this is technology that most enterprises do not have.

In general, we have not seen a mass uptake of DC power equipment for internal datacentre use. The high voltage of DC puts a lot of people off and I think the advantages have failed to outweigh the disadvantages for most firms.

I think the idea of using fresh air is very good; BT has raised a debate there and my view is that companies should be using a mixture of different techniques to cool their datacentres, depending on their geographical location and local climate.

There is no reason why you could not use fresh air as long as you extract the dust out of it. Dehumidifiers can be installed around the building to reduce condensation, but it is a question of how much power do they use, and are you just robbing Peter to pay Paul? Condensation is an ongoing problem with fresh air cooling, but the whole thing needs a sufficient level of education before companies can embrace it."