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. The gas is stored in cylinders, and is released at high velocity out of nozzles uniformly spread across the data center. According to people familiar with the system, the pressure at ING Bank’s data center was higher than expected, and produced a loud sound when rapidly expelled through tiny holes (think about the noise a steam engine releases). The bank monitored the sound and it was very loud, a source familiar with the system told us. “It was as high as their equipment could monitor, over 130dB”. Sound means vibration, and this is what damaged the hard drives. The HDD cases started to vibrate, and the vibration was transmitted to the read/write heads, causing them to go off the data tracks. “The inert gas deployment procedure has severely and surprisingly affected several servers and our storage equipment,” ING said in a press release.