From an article discussing Seagate’s plant in Ireland (where 80% of the company’s read/write heads are produced): an impressive analogy of a HDD’s read/write head.
The dimensions of the head are impressive. With a width of less than a hundred nanometers and a thickness of about ten, it flies above the platter at a speed of up to 15,000 RPM, at a height that’s the equivalent of 40 atoms. If you start multiplying these infinitesimally small numbers, you begin to get an idea of their significance.
Consider this little comparison: if the read/write head were a Boeing 747, and the hard-disk platter were the surface of the Earth:
– The head would fly at Mach 800
– At less than one centimeter from the ground
– And count every blade of grass
– Making fewer than 10 unrecoverable counting errors in an area equivalent to all of Ireland.