Inside Rackspace's UK cloud datacentre

The datacentre has a power usage effectiveness (PUE) rating of 1.7, though Rackspace hopes to lower this to an average of 1.59 once the third data hall is built.

Cooling is achieved via computer room air-conditioning (Crac) units that pass cold air through the underfloor plenum. The current is then lifted into the servers and expelled as hot air at the back. Unlike numerous other datacentres, the racks are not enclosed.

"If we were to box in the cold aisle, it wouldn't give us particularly good efficiency," Gary Boyd, the datacentre operations manager for the facility, said. He explained that Rackspace's use of Crac units means the facility has the air mix in the open areas at the top of the servers. External cooling coils are used to provide cool air when the exterior temperature is below 14°C.

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According to Boyd, Rackspace plans to tweak its cooling approaches for the third data hall, which is in construction at the moment and due to open in August 2011.

The new hall will aim to use free-air cooling from the outside. It will also run power via bus bars attached to overhead metal bars (pictured, top left). The company is considering enclosing the hot aisles of the servers with a plenum so that it has a tighter level of control over how much and where the hot air can mix with the cold.

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The facility's core infrastructure is located on the exterior of its large warehouse. It has multiple containerised diesel generators equipped with sound dampeners, which are designed to reduce noise and so meet the maximum of 70Dba required under local ordinances.

"They come with their own acoustic packs for planning permission," Boyd said.

Also, because integration and manufacture is done off site, it is relatively easy to install the generators on an as-needed basis, he added. This is a requirement for the company, as it expects to expand further.

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Cooling for the facility is achieved by five chillers, which consume 1.5MW of power each. Air is sucked up underneath through cooling grills and water-cooled coils, and then pulled into the facility via the refrigerant chillers. Two further chillers are set to be delivered.

As with any datacentre, security is a priority. The security hut (pictured, bottom right) is used to check the identities of people coming on site during the construction process for Data Hall Three.

See more of ZDNet UK's datacentre tour.

The company keeps around £1.8m worth of spare parts on site so that it can quickly swap out and replace servers in case of hardware faults. Typically, when servers fail it is because of a hard-drive failure, Boyd said. However, Rackspace keeps on-site spares for numerous components, including motherboards, PSUs and RAM.

In addition, the company can provide an integration service for Google's enterprise search tool, the Google Search Appliance, which some customers buy to increase the efficiency of searching through their data.

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