In September 1956, IBM launched the 305 RAMAC (Random Access Method of Accounting and Control), the first commercial computer that used a moving-head hard disk drive (as opposed to sequential access magnetic tape storage).
The RAMAC’s disk storage unit, the IBM 350, weighed over a ton, had to be moved around with forklifts, and was delivered via large cargo airplanes (as above). It stored approximately 5MB of data: five million 8-bit characters on fifty 24-inch-diameter disks, a form of drum memory. It consisted of two independent access arms that moved up and down to select a disk, and in and out to select a recording track, all under servo control. The average time to locate a single record was 600ms (c.f. the seek times for modern hard disk drives of 5-10ms). IBM touted the system as being able to store the equivalent of 64,000 punched cards.
Over a thousand IBM 305 RAMAC systems were built, which were leased for $3,200 per month, equivalent to a purchase price of about $160,000 in 1957 dollars (approximately $1.3m today). The 305 was one of the last vacuum tube computers that IBM built, with production ending in 1961.
A representative for Hitachi Global Storage Technologies (which acquired IBM’s hard disk drive business in 2002), stated in a Wall Street Journal interview in 2006 that the storage capacity of the drive could have been increased beyond 5MB, but IBM’s marketing department was against a larger capacity drive because they were unsure how to sell a product with more storage…(oh, how times have changed).
(HT to Retronaut for this post)