The IBM 350 Disk File was developed under the code-name RAMAC by an IBM San Jose team led by Reynold Johnson. It was announced in 1956 with the then new IBM 305 RAMAC computer.  A variant the IBM 355 Disk File was simultaneous announced with the IBM RAM 650 computer, an enhancement to the IBM 650.


The IBM 350 drive had fifty 24-inch (0.6 m) platters, with a total capacity of five million 6-bit characters (3.75 megabytes).  A single head assembly having two heads was used for access to all the platters, yielding an average access time of just under 1 second.

The RAMAC disk drive created a new level in the computer data hierarchy, today known as secondary storage, less expensive and slower than main memory (then typically core or drum) but faster and more expensive than tape drives.  Subsequently there was a period of about 20 years in which other technologies competed with disks in the secondary storage marketplace, for example tape strips, such as the NCR CRAM, tape cartridges, such as the IBM 3850, and drums, but all ultimately were displaced by HDDs. Today SSDs compete with HDDs in the marketplace.


The IBM 1301 Disk Storage Unit, announced in 1961, introduced the usage of heads having self-acting air bearings (self-flying heads) with one head per each surface of the disks.

Also in 1961, Bryant Computer Products introduced its 4000 series disk drives. These massive units stood 52 inches (1.3 m) tall, 70 inches (1.8 m) wide, and had up to 26 platters, each 39 inches (0.99 m) in diameter, rotating at up to 1,200 rpm. Access times were from 50 to 205 milliseconds (ms). The drive’s total capacity, depending on the number of platters installed, was up to 205,377,600 bytes (205 MB).


The first disk drive to use removable media was the IBM 1311 drive. It was introduced in 1962 using the IBM 1316 disk pack to store two million characters. It was followed by the IBM 2311 (1964) 5 megabyte and IBM 2314 (1965) 29 megabyte disk pack HDDs.


In 1968 Memorex shipped its first first HDD, the Memorex 630, plug compatible to an IBM model 2311 marking the beginning of independent competition (Plug Compatible Manufacturers or PCMs) for HDDs attached to IBM systems. It was followed in 1969 by the Memorex 660, an IBM 2314 compatible, which was OEM’ed to DEC and resold as the RP02.


Removable disk packs

In 1973, IBM introduced the IBM 3340 “Winchester” disk drive, the first significant commercial use of low mass and low load heads with lubricated platters. This technology and its derivatives remained the standard through 2011. Project head Kenneth Haughton named it after the Winchester 30-30 rifle because it was planned to have two 30 MB spindles; however, the actual product shipped with two spindles for data modules of either 35 MB or 70 MB. The name ‘Winchester’ and some derivatives are still common in some non-English speaking countries to generally refer to any hard disks (e.g. Hungary, Russia).