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DISA depends on redundancy

TINKER AIR FORCE BASE, Okla. -- Redundancy - duplication of systems - is a hallmark of the Defense Information Systems Agency.

"The cyber world in which we operate has countless saboteurs and hackers and terrorists, and they pose a continuous threat to the United States," said Anthony L. Purvis, director of DISA's Defense Enterprise Computing Center - Oklahoma City. "Yet our customers expect and demand always-on, no-fail systems and services 24/7/365 despite the potential threats from enemies and weather and natural disasters."

The DECC is housed in Bldg. 3900. Of the 98,000 square feet of floor space in the two-story building, almost half -- 46,000 square feet -- is devoted to the main computer room, which houses dozens of computer server arrays.

Each server is powered by dual electric systems so that if the primary power supply is interrupted, a secondary supply will be activated automatically.

The DECC is connected to two commercial electric substations, so if one goes down the other switches on. If both substations are disrupted, the facility has two pairs of diesel-powered backup generators, a 22,000-gallon diesel fuel tank, and a roomful of huge batteries. During the May 2010 tornadoes that struck the Oklahoma City metro area, repeated power surges "made the electrical environment unstable," Mr. Purvis recalled, so DISA-OKC operated on generator power for almost two weeks until commercial electric service returned to normal.

Within each computer application managed by DISA, there's a "fail-over strategy" in place "so if a site goes down, we can get that data from one site to another." Mr. Purvis related. Similarly, DISA maintains three copies of each DOD enterprise e-mail system it manages; two are local copies and a third is maintained at a geographically remote location.

The main computer room in Bldg. 3900 is temperature controlled and has "hot" aisles and "cold" aisles.

"Hot" aisles are the areas directly behind the server arrays, where heat generated by the computers is discharged by their internal exhaust fans. "Cold" aisles are immediately along the front of the myriad servers. Cold air blows across the face of the server arrays through holes in the floor tiles.

The air is cooled, to 45-52 degrees, by four chillers in the back of the building; on any given day, one pair of chillers is used to cool the air and the other pair is on standby in the event of an emergency.
"A lot of strategy goes into floor management," Mr. Purvis said.

DISA is preparing for a "technical refresh" -- an update of its computer servers -- because the average lifecycle of a computer system is three to five years. The refresher project will start next January, and almost every computer in the main computer room will be replaced with updated units, Mr. Purvis said. The task will take two years to complete at all 13 DISA computing facilities worldwide.

Because of an advancement in technology, two years ago the Oklahoma City DECC staff compressed 14 racks of server arrays down to one rack of equivalent computing capacity, records reflect. "We reduced the physical footprint from 140 square feet of floor space to 4 square feet," Mr. Purvis said. The achievement earned five DECC-OKC employees the agency's Outstanding Achievement in the Computer/Computer Software Field award for 2010.

DISA has "close to 600 employees" in its Oklahoma City operations, Mr. Purvis said. Approximately 500 of them work in Bldg. 3900 and about 100 of them work in Bldg. 201.