A topic that I find eternally fascinating... CNET published a series about the history of harddrives.
A few quotes:
The IBM System 305, the world's first hard drive, debuted in 1956 and relied on the random access method of accounting and control (RAMAC) to store data. This is a side view. The entire device required 50 24-inch diameter platters coated with iron oxide paint mounted on a rotating spindle. It held 5MB, or about 1/100th of the amount in flash cards for cameras today.
"I remember the RAMAC maintenance crew used to stand by and plug in new tubes, because the heat and use would blow them suckers out all day long. It was an adventure to watch the control arm move up and down the disk system. It moved at a speed that you could see--amazing,"
In 1982, Hitachi shipped the first drive with more than 1GB of storage. [...] Six years later, Hitachi shipped a 1.89GB drive made from eight 9.5-inch disks, which reduced the kilogram-to-gigabyte ratio from 121 kilograms per gigabyte to 42.