Essential Guide to Computer Data Storage: From Floppy to DVD, The

Hard Disk Drive

Introduction

Introduced in 1957, the IBM-made random access method of accounting and control (RAMAC) was the first disk drive. It consisted of 50 magnetic disks of 24-inch diameter rotating at 1,200 RPM (rotations per minute).

Two air-bearing supported magnetic heads accessed all 50 disks. The total storage capacity of this system was 5 MB, with a data rate of 12.5 KB/s. The system was typically rented off to the end user for about $130 a month. The system used aluminum sliders, Mu-metal heads, had densities of 20 tpi and 0.002 Mb/in2, and the slider/disk spacing was about 20 micrometers (or 20,000 nm).

This disk drive can be contrasted to its evolutionary disk drive achieved some 40 years later, the IBM Microdrive. The Microdrive ...