Old mines have been converted into industrial spaces for decades, and now data centers. Your first thoughts -- damp, dark, cramped and airless -- couldn't be further from the truth (though these sites do look like a superhero's secret headquarters).
Security is a big payoff for building underground. A data bunker, as underground, highly secure data centers are called, can reside within a shale enclosure, with access points few and far between. There are some considerations for secure data center designs when you build data centers in such physically restrictive environments.
"A lot of underground data centers fail because they approach it like a conventional greenfield data center build. You have to understand the structure, how to expand, etc.," said Dan Golding, vice president of data center operations at Iron Mountain Inc.
At SubTropolis, there's about 17 feet to work with between ledges. The data center follows a layout dictated by 25-foot-square support columns.
The underground data center at SubTropolis in Kansas City, Mo., stays at a constant 65 to 70 degrees Fahrenheit with constant humidity, and offer millions of square feet of floor space. Iron Mountain's Boyers data center stays at about 52 degrees Fahrenheit, and the surrounding limestone absorbs heat thrown out by operating server racks. Clay and shale layers in the mines absorb and seal out water to keep data centers dry.
Former limestone mines offer wide-open horizontal space, not winding caverns deep into the earth. SubTropolis is on the ground-level of a hill that's 100- to 150-feet tall and protects the data center from everything from floods to tornadoes to earthquakes in the New Madrid Fault Line. The mine was "appealing" right away to colocation provider LightEdge Solutions Inc., which had never built underground before, said LightEdge CEO Jim Masterson.
Iron Mountain's Boyers data center is about 220 feet below the surface, but descends gradually to a large horizontal plane. The location has about 3,000 employees in various operations and support roles, including a fire squad and restaurants.
In general, air quality is not difficult to maintain, according to the underground data center operators. Several two-lane roads into the mountain increase security and provide airflow at SubTropolis. Ventilation shafts provide fresh air at Iron Mountain's Boyers location.