History of hard disk drives
In 1953, IBM recognized the immediate application for what it termed a "Random Access File" having high capacity and rapid random access at a relatively low cost. After considering technologies such as wire matrices, rod arrays, drums, drum arrays, etc., the engineers at IBM's San Jose California laboratory invented the hard disk drive. The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory but faster and more expensive than tape drives.
A partially disassembled IBM 350 (RAMAC)
Removable disk packs
Burroughs B-475 Disk Drive (circled)
Seagate 20 MB HDD and Western Digital Controller for PC
The IBM 305 RAMAC was the first commercial computer that used a moving-head hard disk drive for secondary storage. The system was publicly announced on September 14, 1956, with test units already installed at the U.S. Navy and at private corporations. RAMAC stood for "Random Access Method of Accounting and Control", as its design was motivated by the need for real-time accounting in business.
IBM 305 RAMAC system: IBM 305 main system (Processing unit, magnetic process drum, magnetic core register, electronic logical and arithmetic circuits) IBM 370 printer (left), IBM 380 console (right)
One RAMAC storage disk showing head crash damage
IBM 305 at U.S. Army Red River Arsenal. Foreground: two 350 disk drives. Background: 380 console and 305 processing unit
RAMAC mechanism at Computer History Museum