The head flies a few nanometres above the disc
Inside a hard drive, the reader does not touch the platter. It flies on a film of moving air, or helium, a few nanometres up.
Established2 min read
The slider is shaped like a wing. The spinning disc drags gas under it and the gas lifts the head. The first commercial drive, in 1956, flew at a gap you could almost see. By the 2010s the gap on a high-density drive was a few nanometres, comparable to a handful of molecules, which is why a smoke particle is enough to end a disc and why the box is filtered.
Helium drives seal the box and fill it with a lighter gas, so the head can fly with less drag and the platters can be stacked closer. The principle does not change. The memory is a magnetic pattern. The reader is a wing that must never land for long.
Caveats
- Fly height depends on the generation. A few nanometres describes modern high-density drives, not the 1956 machine, and some designs briefly contact on purpose.
- A drive is not designed to run in a vacuum. No gas, no wing, no flight.
Sources
- 1Wood R.. Future hard disk drive systems. Journal of Magnetism and Magnetic Materials 321, 2009.