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Feature - 8 January 2021 (ComputerWeekly)

The clock is ticking on sustainable IT and energy use, and much more can be done to save energy, power and reduce emissions at a datacentre level. So why isn’t it happening?

Datacentres represent a growing share of global power consumption and emissions. An average user PC consumes 1.3 kWh of electricity every three hours, without even going online; transmitting a million static webpage requests per second has been estimated at another 11.610 kilowatts per hour (kWh) – or enough to power 13 US households for a month.

According to Peter Hewkin, founder of UK edge computing company Smart Edge Data Centres (SEDC), many countries at peak times are already facing limited capacity, with the next wave of data-hungry digital growth on the way. But he also estimates that at least 85% of data stored by UK limited companies, and therefore 85% of data now kept in conventional datacentres or server rooms, could be switched off when not required – and kept in “warm” storage.

“Current year’s accounts should be accessible all the time, but not the remaining six years’,” he points out. “If a datacentre currently consumes 1MW every hour, only 150kW every hour might be required to support the critical data.”

Consumption of 1MW of energy 24 hours a day at £80 per MWh might work out at around £700,000 a year. With warm storage making data accessible on business days only (excluding bank holidays) or 252 days a year, savings already reach 30%.

If data access can be restricted to a named two hours from Monday to Friday, that works out at just 506 hours a year – less than six percent of the current global standard of 8,760 hours.

“Some 15% of data needs to be available 24 hours a day, seven days a week, but we still only come to a figure of 1,820 hours,” says Hewkin, adding that better pricing might be negotiated with suppliers for staying out of “red” peak times, for instance after 4pm and before 8pm. “This represents nearly an 80% saving on total consumption and CO2 emissions.”

For green and orange band pricing, he believes a price of around £60/MWh could be realistic, with even £20/MWh potentially achievable if only two hours a day at green band pricing are required.

“Using 150kW 24x7 at £80/MWh our annual electricity charge will be around £105,120. The remaining 850kW are only used for 506 hours a year at £60/MWh, equating to £25,806. The annual total is £130,926 compared to £700,800 currently. This represents a saving of 81%,” he says.

Electricity consumption

John Booth, managing director of consultancy Carbon3IT, estimates datacentres, including colocation facilities, account for at least 12% of UK electricity consumption, or 41.11TWh a year.

Cisco has previously forecast global cloud IP traffic to exceed 14.1 zettabytes (ZB) by the end of 2020; IDC’s Seagate sponsored Data Age 2025 report projects overall data growth of 30% a year to hit 175 ZB – with data stored of 7.5ZB, up from 1.1ZB in 2019. Hyperscaler growth alone is expected to continue at a CAGR of 2% a year until 2025, according to ResearchAnd Markets.

Datacentre efficiency: a work in progress

Sustainability innovations of all kinds do continue to increase efficiency in datacentres, but there’s clearly still scope for other approaches.

French researchers Issam Raïs, Anne-Cécile Orgerie and Martin Quinson, writing in peer-reviewed journal Concurrency and computation practice and experience, quantified the likely impact of various shutdown techniques in the datacentre.

Operators have often been reluctant to reduce their number of switched-on servers because of worries about reactivity and hardware failures, and misjudgements about energy gain, they suggest.

The team simulated various production infrastructures and machine configurations under different shutdown policies and workload predictions. These include actual server switch-off and hibernation modes, and suspend-to-disk and suspend-to-RAM techniques, heterogeneous processing, and boot-up costs in time and energy as well as server lifetime, as well as looking at energy-aware algorithms (in related work).

“Shutdown techniques can save at least 84% of energy otherwise lost to power idle nodes. This remains true for prospective energy-proportional hardware and even aggressive shutdown policies do not impact hardware lifetimes,” they write.

SEDC’s Hewkin notes that some forecasts still estimate that datacentre power consumption could devour 20% of UK generation in the next few years if current trends continue.

Yet most data generated is only used a few times, sometimes only once, and then stored forever “just in case”, such as bank accounts or a company’s trading accounts. Banks have already started moving older consumer data into “cold” inaccessible storage...


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