https://motherboard.vice.com/read/a-loud-sound-just-shut-down-a-banks-data-center-for-10-hours
ING Bank's main data center in Bucharest, Romania, was severely damaged over the weekend during a fire extinguishing test. In what is a very rare but known phenomenon, it was the loud sound of inert gas being released that destroyed dozens of hard drives. The site is currently offline and the bank relies solely on its backup data center, located within a couple of miles' proximity.
"The drill went as designed, but we had collateral damage", ING's spokeswoman in Romania told me, confirming the inert gas issue. Local clients were unable to use debit cards and to perform online banking operations on Saturday between 1PM and 11PM because of the test. "Our team is investigating the incident," she said.
The purpose of the drill was to see how the data center's fire suppression system worked. Data centers typically rely on inert gas to protect the equipment in the event of a fire, as the substance does not chemically damage electronics, and the gas only slightly decreases the temperature within the data center.
(Score: 3, Informative) by sjames on Monday September 12 2016, @09:57PM
It's production was banned, but many systems installed before that still have it. For years after, there was a grey market for halon in tanks removed from decommissioned or updated data centers.