Supermarket giant Tesco is using steam-age technology to
keep its 21st century datacentre running during power
failures.
The retailer is one of a handful of companies in the country
using a
flywheel to
store electricity for powering down servers in an emergency.
The flywheel is one of the more radical elements in Tesco's
10-year blueprint to
reduce the power consumption in its datacentre.
Nick Folkes, IT director at Tesco, has workedon the project for
the past 18 months.
"Last year, we realised our electricity costs were going through
the roof. We needed to do something radical. We were already using
virtualisation for our mainframe and high-end Unix systems, but
we had to tackle energy waste on our Intel servers."
Tesco was able to keep its existing datacentre fully operational
as it installed the new hardware, cooling and software components.
Tesco is deploying the final servers this month and the roll-out
will be completed in April.
Environmentally-friendly
option
Tesco is using the flywheel toreplace traditional
uninterruptible power supplies, which require a bank of
environmentally-unfriendly lead-acid batteries to supply back-up
power to the datacentre.
The flywheel system claims to be 98% energy efficient. The
wheels rotate at 7,200rpm to store energy, which is converted to
electricity, when there is a power failure.
Folkes says the kinetic system is able to provide 25 seconds of
power, enough to enable the servers to power down safely.
Tesco has invested in new power generators that can startup in
less than 20 seconds, fast enough to power up the datacentre when
there is a prolonged power cut."Our old generators were slow and
took 60 seconds to start,"says Folkes.
Tesco has also upgraded its datacentre cooling, using a hot isle
containment system supplied by APC to improve cooling efficiency.
The system uses fans on the blade servers to expel air into a
sealed area between rows of racks called "hot isles", making
cooling more efficient and predictable because the hot air is
contained in one place. Experts saythis reduces thelikelihood of
hot spots developing in the datacentre, which can cause components
to overheat and fail.
According to Folkes, the hot isle technology allows Tesco to run
more blade servers per rack than is normally possible. "We can use
30kW per rack, compared with 2-3kW per rack with traditional
datacentre cooling," he says.
| Flywheel energy storage |
|---|
Flywheel energy storage systems store kinetic energy, ie the
energy produced by motion, by constantly spinning a compact rotor
in a low-friction environment. When short-term back-up power is
required the rotor's inertia allows it to continue spinning and the
resulting kinetic energy is converted to electricity via a
generator. Texas-based
Active Power has
developed an integrated UPS and DC power supply,
CleanSource Flywheel, as an alternative to chemical
batteries. Source: Active
Power |
Server
virtualisation
Tesco has refitted its datacentre with HP Bladeserver hardware,
an HP SAN and Citrix networking.
It has used Citrix Xenserver as its
virtualisation platform. Folkes says he selected Citrix over
market leaderVMware because the Citrix product is licenced on a per
server basis, whereas VMware uses per core licensing.
The Citrix technology has allowed Tesco to reduce the number of
Intel servers to just over 180 - down from more than 1,500 when the
project began. The servers are also running more applications,
making them more energy efficient. Folkes says Tesco is now seeing
70% utilisation on its Intel servers, compared with 6% before.
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