The Tom’s Hardware “picture story” Where Do Hard Drive Heads Come From? addresses something that always amazed me: how do hard drives work so reliably on such a small scale, all while spinning at >7200 rpm?
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.
Wow.
