On the r/sysadmin section of Reddit, I recently participated in a discussion about hard disk drive failures from smoke, which forms the basis for this article. Since this is not a topic we normally cover on WeLiveSecurity, a little bit of background may be helpful.
Conventional hard disk drives work by spinning a series of aluminum or glass platters on a spindle driven by an electric motor. And when spun up, they are going pretty fast and with incredibly fine tolerances: hard disk drives used in servers spin their platters at up to 15,000 revolutions per minute (RPM), which works out to around 150 mph (or about 240 kph, for the metrically minded). Just barely above and below these platters float minuscule read-write heads, each less than a millimeter wide, at the end of an actuator arm. How far apart do the actuator arms place the heads from the platters? As little as 3 nanometers, or about 1/25,000th the thickness of a human hair. Read-write heads themselves are so small that they are manufactured using similar technologies to those used to make CPUs. All of these parts come together in a device that looks not too different from a record player, aside from its size.
At the dawn of the hard disk drive era, the distance between the read-write heads and the platters inside the hard drive enclosure was much greater, so much so that smoke particles, often less than a micron in size, might pass between the platters and read-write heads with ease. One can imagine that mainframe computers with high-pressure-air- or water-cooling systems in a computer center would have air filtering systems similar to a clean room, with air filters serviced regularly according to a schedule. For that matter: SAGE, one of the earliest distributed military computer systems, had built-in cigarette lighters and ashtrays.