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Energy-aware computing: New ways to keep cool
By Jamie Beckett, Jan. 2006
Soaring demand for information technology, increasingly powerful microprocessors and the
growing popularity of compact blade servers means that data centers are more densely packed
than ever – and that means a tremendous demand for cooling.
There are two primary ways to reduce the costs of cooling data centers: Design more energyefficient data centers and design machines that generate less heat. HP Labs is developing both.
'We believe in looking at energy-aware computing holistically – from the chips to the servers to
the data centers to the services that run in the data centers," says John Sontag TITLE?.
This month, HP is announcing several new products and services, including Data Center Thermal
Assessment Services, that grew in part from these research efforts.
Managing energy consumption
Researchers are now pursuing new frontiers -- designing hardware that consumes less energy,
deploying computing workloads in a more energy-efficient manner, developing systems for
dynamically allocating cooling resources and creating sophisticated sensing systems to control
cooling.
The goal: To provide better energy efficiency, increase data center uptime and to allow data
centers to operate at higher power densities so users can get the most out of their IT
investments.
"The key technical challenge of an always-on compute utility is the management of energy as a
resource," says Chandrakant Patel, who leads the HP Labs component of the "Cool Team," a
network of technologists across HP who are developing energy-management technologies.
Generating less heat
Partha Ranganathan is focused on the subtraction side of the energy equation. He's investigating
technologies that will squeeze inefficiencies out of current systems to reduce the amount of heat
they generate.
One approach involves introducing heterogeneity. Rather than using identical processors on
multi-core chips, for example, Ranganathan says his research has shown that mixing different
processors on a chip can reduce energy consumption by 40 percent with almost no effect on
performance. (See related technical paper.)
How so? By assigning tasks to whichever processor can perform it most efficiently.
Similar principles apply individual systems in a blade server, he says.
Managing a power budget
Ranganathan and his team have also developed an algorithm for workload placement and
resource provisioning that, in essence, directs the most heat-intensive workloads to the coolest
location in the data center.
In addition, researchers have prototyped a system that can work with 20 to 30 percent reduced
cooling by managing a heat "budget" across an entire collection of systems -- allocating
resources according the urgency of a job, its importance to the organization, service-level
agreements or other factors.
The prototype works in much the way any other budget does, Ranganathan says. “My manager
knows that potentially, every one in his team could order a new PC in a quarter, but he does not
plan his purchase budget for that worst case. He just plans it for a likely scenario based on past
experience. You should be able to plan for heat in the same way.”
Adding precision
Chandrakant Patel and his team are focused on better managing what heat a data center
generates. They've designed a dynamic thermal management system aimed at more closely
monitoring and controlling temperature in a data center.
Traditional systems measure data center temperature at the hot-air return of air conditioning units
instead at the heat source – the racks. Because controls are imprecise, these data centers are
often operated at less-than maximum capacity to avoid overheating. That's an expensive
proposition.
The researchers' solution uses a distributed sensor network attached to standard racks, providing
a direct measurement of the environment where it is most useful. Experiments to compare the
HP Labs solution with a conventional system show potential savings of more than 50 percent in
cooling costs.
"We're putting the control point where it should be," says Cullen Bash, a "Cool Team" researcher
in HP Labs. "And instead of relying on a single sensor, we're controlling cooling based on many
sensors."
Increased availability
HP Labs' dynamic smart cooling technology processes sensor data to determine how best to
allocate cooling resources to maintain specified rack temperatures.
"It's not just that we can save energy. By monitoring temperature close to the heat source, we can
react a lot faster," Bash says.
That adds up to increased availability for computing systems. Not only do system uptimes
increase, but IT managers can run equipment at higher power densities, which allows them to get
more use out of existing machines. Bottom line: Businesses can get the most out of their IT
investments.
Earlier work, next steps
Energy-aware computing is not a new problem for HP Labs, which has been working in this area
since the early 1990s.
In the process, they've found some novel ways to use old technologies -- including HP's classic
inkjet technology, which they put to use for targeted spray cooling of microprocessors. Working
with engineers in HP's printing and imaging group and elsewhere in the company, the
researchers re-configured the inkjet head to spray tiny droplets of dielectric liquid coolant instead
of ink
Later, researchers developed a technology that provided the basis for HP's recently announced
Data Center Thermal Assessment Services. This service, already in use by several customers,
assesses the unique thermal conditions in a data center and develops recommendations for
better cooling.
A follow-on technology called dynamic smart cooling is used in HP Labs' Palo Alto, CA, data
center. In the lab's 100-rack data center, dynamic smart cooling has generated savings of 60
percent.
The next step for researchers is merge all their work into a single integrated system.
What we're doing is using the most efficient ways of distributing computing resources," says
Patel, "then threading those together in a stack in such a way that we're minimizing energy
consumption."