Balancing Up, Out, And Density In Data Centers
A number of factors are necessary to find the data center’s sweet spot.
John Peterson is a program manager with AECOM specializing in mission critical facilities. His experience and responsibilities include all aspects of mission critical systems designs and coordination for a wide variety of data center types and sizes. Mr. Peterson’s background also includes experience in project management, construction management, and he leads mission critical technical training. As one of the leaders of the mission critical business line for AECOM, he tracks and assists the application of high reliability and efficient solutions for government and commercial clients throughout the world.
Data centers have become larger, more dense, and taller over the last decade. This growth is fueled by the expansion of data; of course, as every industry realizes how data can be used to improve their processes and every company collects and processes more information than ever before.
But the deciding points of whether to go wider, taller, or denser has been debated as land, power, and construction have changed over time as well. And although many data centers have similarities and might even look the same, very few are created equal. The decisions around the balance of up, out, and density also revolve around security, flexibility, and the core infrastructure that supports the business needs; however for simplification we will examine the general progress and advice to best suit the overall data center market.
Land: a shrinking resource?
The amount of land available to us is finite and we need to carefully manage how the land is deployed for the many things around us. This has led to the development of land use plans for cities across the U.S., and with the explosion of data this now includes adjustments for more land devoted to data centers. Some areas are already thick with data centers with Ashburn, Virginia, being the densest and growing denser every year.
Yet just because data centers are abundant in a region does not mean there isn’t space to grow. Even in Northern Virginia the number of data centers could double before land for them was exhausted. In many markets, the space shortage causes land prices to increase steadily as the better land choices shrink; this trend will more than likely continue in the future as all types of buildings, infrastructure, and more are developed in existing and new spaces around hubs and cities to provide for the local growing needs.
Land for data centers also follows the number one rule in real estate for nearly a century: location, location, location. In some places land has been advertised as free, as there are enough incentives from the local jurisdictions to offset the land cost. Other locations just outside of fiber-rich areas are growing as well, with the land prices at about half of that for a location just a few miles away; in Ashburn, Virginia, the prices have steadily creeped upward but thus far few data center owners are willing to spend $2 million per acre just for the proximity. Most have learned that the surrounding locations in Northern Virginia are quite close enough with average land prices closer to less than $500,000. Around the nation, counties have followed what brings a data center to their town, and land is one of the incentives brokered to sweeten the lure for owners.
Instead of land being scarce, the driving factor is a perceived shortage of the preferred locations for data centers — the sites that have everything on the data center wish list: enough ready land, inexpensive power, water for cooling, fiber density, tax incentives, services, plentiful workforce, and more. And this shortage of premium locations with enough land to develop a new data center creates the desire to increase density or explore going up.
Going up: structure and utilities
Typical data centers need stout structural support to ensure that the heavy equipment inside will be able to be supported without any possible issues. Increased density of IT equipment doesn’t just mean the power and cooling needs, but the servers themselves are physically weighing more than before. For a data center structural design this simply means that either the floor slab has to be stronger or the load needs to be spread across more of the floor to keep it from sagging or causing point penetrations failures.
With a single floor design, a slab-on-grade is an easy solution. Multiple floors entail a bit more thought and analysis, as a second floor supporting 5,000-lb. cabinets as well as the structural ceiling for the first floor that carries the conduits, cabling, and more requires robust structures that add to the construction costs and time, whether or not there is a raised floor. The UPS and batteries that are likely on the same floor weigh just as much as the cabinets and used to be the only equipment in the data center that caused structural designers to worry about weight.
With any tall building, the need to resist lateral loads is greater, and with the heavier load of a data center this increases the supporting assembly even more. Add in that there are likely requirements to resist severe weather, such as tornados, or other threats, and the structure is then engineered to be even stouter.
The increases of costs aren’t just due to the structural adjustments but also to the additional needs for the building to function, such as stairs and elevators. The construction of multi-level facilities generally takes longer and costs more depending on the height, with every additional story increasing the cost cumulatively. At a certain point the cost to increase has diminishing returns, which some have found to be at three stories. To design a generic data center up certainly makes sense when the cost of the land is greater than about $800,000 per acre; with land at less than this amount the costs to increase the building height start to weigh against the increased height.
Regardless of the cost as the determining factor, building higher has been done in a cost-effective manner by many of the larger data center owners. There are also numerous benefits that relate to functionality improvements, such as how power and cooling are fed through the building as well as easier egress through the facility. Cost efficiencies can include reduction of time for the site to be permitted and prepared for a smaller footprint. The simplicity of a repeated data center floor plate can speed the construction of the initial core and shell, with more of the fit-out to be phased separately or even delayed until the data center space is needed.
Going dense: power & cooling
Another option that continues to grow year-over-year is not going up or out at all, but solving the need for more compute by increasing IT density. The computing power density has risen from 5 kW per rack a decade ago to an average closer to 15 kW per rack for today’s new data centers. The industry has steadily looked for more options, as the desire for more space requires more capital investment, even as the requirements for more power and cooling grows linearly with the density.
Densifying, like going with higher data centers, increases the amount of power per acre as well as the cooling needs. There are solutions for even the most challenging power and cooling needs, with many specially developed super computing platforms still in operation today.
However, the need for density isn’t typically derived by the data center manager or owner, but by those looking for a home for their servers. The data center may have flexibility to achieve 25 kW per rack or higher using only air cooling solutions and 70 kW and more with liquid cooling, but the data center may never reach these lofty heights if the endusers aren’t willing to use the equipment and configurations that will take them this high.
The costs to increase density with a new building also depend on the kW per rack, as there is a perceived threshold to utilize water-based cooling at the server or rack level once above a certain power range (typically 15 to 30 kW per rack, depending on the white space configuration).
Data centers with more flexibility and options for higher density are likely to be more comprehensive and be the better solution for clients, no matter if they ever actually deploy with equipment that match those densities during their lifespan.
Striking the balance
When it comes to finding a sweet spot for a data center, there are a number of factors that go into the overall equation to determine the size, height, and density. Governments and developers in many cities and markets have said there has been a need to look into the future of what may be available around us and how best to utilize those resources. The sites and land for data centers is no different, with long-term planning already underway by the major data center businesses acquiring enough land to develop large new campuses in the major markets.
Depending on location building higher can yield efficiencies in cost and operations and there can be further savings based on how the power and cooling are provided in a similarly stacked method. However, when land is relatively abundant in places with enticing incentives and around plentiful fiber, the need to add even a second story may not outweigh the costs to a single level, perhaps with scooters to glide down those long corridors.
Since the top 10 data center owners have banked over 2,700 acres of land they will likely track the pace of development to necessitate going up, out, or denser. And naturally they will be able to watch what their neighbors are doing, for cost as well as these factors and more, to evaluate how best to proceed with their next facility.