1953: IBM 650 Magnetic Drum Calculator
The IBM 650 Magnetic Drum Calculator was notable for its high-speed magnetic storage drum permitting rapid access to data. This was intended to be a less powerful version of the 701 Computer, but its easy configuration caused the system to be one of the best selling computers of the 1950's, with about 2000 units installed before it was discontinued in the early 1960's. By comparison the 701's achieved only 19 installations over a three year period.
Magnetic drum storage was supplemented by magnetic disc storage with the IBM 305 RAMAC in 1956. This set off a period of competition between these two storage media, not unlike the Gramophone battle 50 years earlier. Magnetic disc storage ultimately prevailed for the same reason- the inefficient wasted space inside a drum.