
One
of the data halls at Cavern Technologies in Kansas, which offers few
clues that the facility is 75 feet below ground. (Photo: Cavern
Technologies)
The Pros and Cons of Underground Data Centers
October 9th, 2013
By: Rich Miller

The
entrance to the Cavern Technologies data center in Lenexa, Kansas,
which houses its customer servers more than 75 feet underground. The
company is among a growing number of data bunkers storing data for
high-security clients. (Photo: Cavern Technologies)
ORLANDO, Fla. - The data bunker industry is growing,
as more customers seek out ultra-secure underground hosting for their
IT operations. Operators of subterranean server farms say these
environments are similar to above-ground facilities, but they often must
address misperceptions about underground sites, many of which are
housed in former limestone mines.
The emergence of underground data centers was the focus of a session
at last week’s Data Center World Fall conference, in which several
experts discussed the advantages and challenges of underground data
centers, and offered tips to consider when evaluating a data bunker.
“The underground data center space is experiencing rapid growth due
to the efficiency and speed to market it offers,” said John Clune, the
president of
Cavern Technologies,
which operates a data center in a limestone mine in Lenexa, Kansas.
“One of the bigger challenges has been the perception of underground
data centers. People are imagining a tight cubbyhole with a guy with a
light on his helmet. The reality is that we’ve got 18 foot ceilings.”
Cavern Technologies is among a cluster of underground facilities in the Midwest, which also includes
SubTropolis,
The Mountain Complex and
SpringNet Underground in Missouri; and the
InfoBunker and
U.S. Secure Hosting in Iowa.
Tips from Data Bunker Veterans
Not all underground data centers are created equal, and potential
customers need to shop carefully and be mindful of the differences
between traditional and underground facilities, according to architect
Kerry Knott of Bell/Knott & Associates. Knott has worked on a number
of underground business parks and data centers in Kansas and Missouri,
and offers some insights into evaluating a data bunker.
“Data center buildouts are a good use for these kind of facilities,”
said Knott. “Once the data center is built, if you take someone in there
blindfolded, they’d never know they were underground. You’ve got the
same equipment; it’s just been an underground facility.”
But there are some differences. Here are some pros and cons to consider with facilities built in limestone mines:
Speed to Market: Clune says Cavern was recently able
to deploy 5,000 square feet of data center space for a client in just
60 days. “The speed to market is impressive in the underground,” said
Clune. One factor is that there’s no need to build or adapt a shell, as
the underground space has already been created and all that is needed is
the framing and buildout of the data halls. Another benefit is
permitting from local officials. “In every underground I’ve worked with,
we have had a blanket permit” once the initial underground space is
created, said Knott. “It’s one of the advantages of underground
structures. That could be an 8 to 10 week savings.” Another benefit is
that construction can continue year-round, with no weather delays.
Construction Costs: Underground data centers can
also be cheaper, Knott said, since there’s no expense to construct a
concrete shell. Subterranean structures also offer potential savings on
disaster-proofing, especially in the Midwest. “To build a tornado-proof
building above ground can cost an extra $100 a square foot,” said Knott,
who added that customers often inquire about other types of disasters.
“People are concerned about collapse, and they’re worried about
earthquakes,” he said. “An underground space, unlike the building above
ground, doesn’t move and doesn’t need to be reinforced. An earthquake
doesn’t affect the enclosure at all, but you do have to brace the
improvements.”
Facility History and Origin: Recently-built
underground facilities are usually appropriate, but those that were
mined in the 1960s and earlier may not be. “To be an acceptable space
for a data center, it has to have been mined for commercial
development,” says Knott. “The limestone has to be preserved in the
proper thickness and have structural integrity. The room size is also
important, because the columnar support will be rock columns that may be
25 to 30 feet in diameter.”
The size and placement of these columns impacts the technical space.
“Optimizing the layout within the property is essential,” said Knott.
“It’s tough to get 90-degree corners with underground columns, so you
have to be creative, since almost all your equipment is square. With the
restrictions of the columns and placement of the corridor, you have to
work with what you have. It can be awkward if these are haphazardly
shaped.”
Cooling and Ventilation: Underground spaces are
naturally cool, but that doesn’t mean they’ll stay that way once you
fill them with servers. “Heat rejection is the biggest concern and the
biggest challenge,” said Knott. “Most underground spaces have their own
fresh air and ventilation system, but that’s generally for comfort
rather than the kind of heat we’re putting into the space with the data
center. Your options are to drill (ventilation) holes up through the top
or horizontally to the exterior.”
Placement of Mechanical Equipment: Some mechanical
and electrical equipment requires ventilation and must be housed in an
exterior yard. There are several options to address this, which
customers must consider if their goal is disaster avoidance, as this
equipment will be more exposed. “Generators and air-cooled chillers can
be placed against an exterior wall or protected with an outside wall,”
said Knott. “You can also build another underground chamber to house
them.” Another issue to consider is fire suppression systems, and what
happens with water in the event the system is ever discharged in part of
the facility.
Staff Considerations: There won’t be any daylight in
an underground data center, but that’s not different from many
above-ground data centers, Knott says. A bigger concern for staff might
be parking, as underground facilities can be large, and that sometimes
means that parking areas are a significant distance from the data
center.

John
Clune, President of Cavern Technologies, a Midwestern underground data
center, talks about the pros and cons of underground data centers. While
the underground temperature is a consistent 68 degrees, the data center
engineers do have to accommodate for waste heat from servers and other
gear. (Photo by Colleen Miller.)

Rich
Miller is the founder and editor-in-chief of Data Center Knowledge, and
has been reporting on the data center sector since 2000. He has tracked
the growing impact of high-density computing on the power and cooling
of data centers, and the resulting push for improved energy efficiency
in these facilities.