Google warns of spiralling hardware energy costs

The electrical costs of running today's computers could end up far greater than the initial hardware price tag if their power performance doesn't improve, according to a Google engineer.

That situation that wouldn't bode well for Google, which relies on thousands of its own servers.

Luiz Andre Barroso, who previously designed processors for DEC, said in a September paper published in the Association for Computing Machinery's Queue: "If performance per watt is to remain constant over the next few years, power costs could easily overtake hardware costs, possibly by a large margin.

"The possibility of computer equipment power consumption spiralling out of control could have serious consequences for the overall affordability of computing, not to mention the overall health of the planet."

Barroso's view is likely to go over well at Sun, which has just launched its Sun Fire T2000 server, whose 72W UltraSparc T1 Niagara processor performs more work per watt than rivals. Indeed, the "Piranha" processor Barroso helped design at DEC, which never made it to market, is similar in some ways to Niagara, including its use of eight cores on one chip.

To address the power problem, Barroso suggests the very approach Sun has taken with Niagara - processors that can simultaneously execute many instruction sequences. Typical server chips today can execute one, two or sometimes four threads, but Niagara's eight cores can execute 32 threads.

Power has also become an issue in the years-old rivalry between Intel and AMD. AMD's Opteron server processor consumes a maximum of 95W, while Intel's Xeon consumes between 110W and 165W. Other components also draw power, but Barroso observes that in low-end servers, the processor typically accounts for 50 per cent to 60 per cent of the total consumption.

Over the last three generations of Google's computing infrastructure, performance has nearly doubled, Barroso said. But because performance per watt remained nearly unchanged, that means electricity consumption has also almost doubled.

If server power consumption grows 20 per cent per year, the four-year cost of a server's electricity bill will be larger than the $3,000 initial price of a typical low-end server with x86 processors. Google's data centre is populated chiefly with such machines. But if power consumption grows at 50 per cent per year, "power costs by the end of the decade would dwarf server prices," even without power increasing beyond its current nine cents (five pence) per kilowatt-hour cost, Barroso said.

Barroso's suggested solution is to use heavily multithreaded processors that can execute many threads. His term for the approach, "chip multiprocessor technology" (CMP), is close to the "chip multithreading" term Sun employs.

"The computing industry is ready to embrace chip multiprocessing as the mainstream solution for the desktop and server markets," Barroso argues, but acknowledges that there have been significant barriers.

But he warned even chip multiprocessing is only a temporary solution for the next two or three generations of chips and said "fundamental" circuit and architectural innovations are needed to address the long-term problem.

Stephen Shankland writes for CNET News.com