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Navigating Data Center Site Selection and Design

Each data center’s design - and the decision of where to locate it - will differ according to the needs of its end user.

Data Centers 2015
The popular image of a data center is often as exotic as it is misleading. Granted, some really are as portrayed in the movies: high-tech bunkers hewn out of remote mountains. But most are not, and the reality is that both the centers themselves and their locations can differ enormously.

While it’s true that these high-security, environmentally controlled facilities are rarely marked on maps and often lie behind deliberately anonymous exteriors, the desire for a low profile is just one of many factors considered by data center developers when choosing a location.

Each data center’s design will vary according to its end user, and each developer will have a different mix of priorities — from baseline cost to security and transport links — ensuring that no two projects will be the same.

These facilities, which house the countless servers that together power both the Internet and the global financial system, are a critical part of the interconnected infrastructure around our planet. But what determines where they are sited?
…any potential data center location must have two things to even be considered: a truly reliable, high-capacity power supply and communications connectivity that delivers speed plus diversity.
The Bare Essentials
While many infrastructure projects link cities — think roads, railways, pipelines, and airports — data centers need not be physically close to the users of the technology they support.

If, in theory, they could be sited anywhere, in practice, site selection is invariably determined by a series of technical considerations. No matter what other variables go into the developer’s decision matrix, any potential data center location must have two things to even be considered: a truly reliable, high-capacity power supply and communications connectivity that delivers speed plus diversity.

A loss of electrical power would clearly be disastrous for a data center, so all are fitted with backup generators and an uninterruptible power supply as standard. Nevertheless, a proven and reliable power grid is a high priority for a data center location.

This does not mean that a developer will automatically choose an urban location over a rural one. True, urban areas will have a power infrastructure already in place, and are likely to have alternative sources of power as well as resilient communication connections. While an urban location may have easy access to the existing power grid, this says nothing about the reliability of the power supply, nor its availability. Conversely, a data center sited in a rural area will usually be purpose-built, and in conjunction with utility providers, to ensure it has the most advanced connectivity and most robust power supply.

Security Is Essential
Security of power supply is only one of the concerns influencing data center design and site selection. While the servers themselves are designed to be resilient — both to cyber attack and power outages — resilience is often built into the design of data center buildings too.
While an urban location may have easy access to the existing power grid, this says nothing about the reliability of the power supply, nor its availability.
Banking service providers and governments — for whom just a few minutes of downtime could have dire consequences — often demand the highest level of resilience. This tends to mean high levels of duplication of infrastructure, commonly referred to as redundancy, which carries a cost premium.

But in physical terms it can also mean building a “bomb-proof” data center. Developers whose risk assessment may include a terrorist attack as much as a hacker-led one may specify that the site be reinforced with steel and concrete, or even sited underground.

In addition to the obvious security measures expected at a sensitive site — such as a high-security perimeter fence — there is an array of structural techniques that can be used to make the data center itself resistant to physical attacks. Known as “hardening,” these techniques can range from adding fortified blast walls to installing layered countermeasures to prevent intruders.

Human threats can vary greatly, meaning a comprehensive hardening program will need to be able to counter both the brute force of an exterior physical attack — such as a rogue vehicle penetrating the outer perimeter — as well as interior attacks. As a result, many facilities incorporate attack-rated walls, vault-type doors, biometrics, and mantraps to protect the various internal areas of the building.

Of course data centers don’t need to be built on a new site to be high security. While a custom-built data center can be fitted with the latest in intruder-prevention measures, some centers have been built in pre-existing secure sites. One of the best known is the headquarters of the Swedish ISP Bahnhof, built in a former nuclear bunker. The site, which was once a Cold War command center, is in a series of granite caves 100 feet beneath a park in Stockholm.
…structural techniques can be used to make the data center itself resistant to physical attacks. Known as “hardening,” these techniques can range from adding fortified blast walls to installing layered countermeasures to prevent intruders.
Similar sites exist in former military bunkers in Switzerland, and in the British city of Manchester a data center operates in a former Bank of England gold bullion vault. The site is 25 feet underground, has granite walls six feet thick, and a 12-tonne bomb-proof door.

Weather and Geological Threats
If the threat of physical attack is hard to quantify, there are other risks to a data center’s integrity that can be calculated with a higher degree of precision, i.e., extreme weather and seismic activity. Of course all data centers will be sited away from flood plains, and far from areas of historic mining activity in order to prevent the risk of subsidence.

The hurricane threat on the East Coast of the U.S. is a crucial factor both in the siting and design of data centers. Sites in the lee of natural landscape features will be sought after, and the buildings themselves will be designed to withstand very high wind loads. In Northern States, data centers will be designed to cope with heavy accumulations of snow on the roof and walls; and on the West Coast and in areas of seismic activity, designs will include the very latest earthquake-resistance technology.

How much protection a data center developer seeks from this sort of natural threat will depend on two key factors: who the data center will be operated by/for and the cost. The greater a data center’s resilience to these natural threats, the greater the cost. Those clients seeking the highest levels of redundancy will want a data center impervious to “once in a century” weather events. However, a developer with a more limited budget for hardening may settle for the ability to withstand “once in a decade” storms.

The Key Metric
Data center efficiency is frequently judged on the facility’s cost per watt of electricity consumed. This yardstick can be affected by countless factors — from the design of the building itself to the density with which the servers are packed together to how they are cooled.
End users seeking the highest levels of redundancy will want a data center impervious to “once in a century” weather events. However, a developer with a more limited budget for hardening may settle for the ability to withstand “once in a decade” storms.
Servers generate significant heat when in operation — hence cold regions hold an obvious appeal for data center developers. Sites like Facebook’s 30,000-square-meter facility in Sweden are able to use outside air for cooling for 10 months of the year, and such free cooling clearly provides a huge cost savings.

Technology and site design are crucial to a data center’s cost per watt performance, but so too is the cost of the land, as well as construction and permitting costs. Many local authorities offer tax breaks to attract data centers to their regions, for reasons of prestige and job creation. They can offer other incentives too, such as competitive utility costs or reduced sales tax on major equipment.

The speed at which a site can be developed is also a significant factor. With the global demand for data rising every month, speed to market is crucial. A location where the planning or construction process is likely to be longer will have a higher opportunity cost than a rival site that’s able to come online and start generating revenue sooner.

But no developer will chose a site on cost alone. And while remote rural areas may offer the cheapest land, proximity to urban areas makes it easier to attract the skilled workforce needed both to build and run a large facility.

The importance of good transportation links shouldn’t be underestimated either. A big facility will employ up to 100 staff, so good road links are a must, even if security concerns mean a data center is likely to be set back from a high-speed road such as a freeway.
As server density increases, data center developers are less likely to run out of physical space than they are to run out of the power needed to run them, or the ability to cool them sufficiently.
The Future
These cost variables are being shifted by the constantly improving technology of the servers themselves, and their associated IT infrastructure. The cost per watt is being driven down as servers become more efficient — both in terms of power consumption and the density at which they can work optimally.

Technological advances, such as the arrival of highly efficient water-cooling systems, are allowing data centers to pack ever more servers into the same space, and this trend is set to continue. But there’s no sign yet of data center developers seeking smaller sites — with many new facilities being designed with plenty of spare capacity.

As server density increases, data center developers are less likely to run out of physical space than they are to run out of the power needed to run them, or the ability to cool them sufficiently. In the future, the ability to ramp up the power supply could become the single most important requirement for a data center location.

Data centers are already estimated to consume 3 percent of the world’s electricity. While the impact on the power grid of the growing demand for data is being mitigated by advances in server technology, the IT giant Cisco projects that global data center traffic will triple in just a five-year period. With global data demand increasing at breakneck speed, innovation in both server technology and data center design is essential to ensure this vital infrastructure keeps up.
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