History of IBM magnetic disk drives

Few products in history have enjoyed such spectacular declines in cost and physical size along with equally dramatic improvements in capacity and performance.

[5] By 1996, IBM had stopped making hard disk drives unique to its systems and was offering all its HDDs as an OEM.

The RAMAC unit weighs about one ton, has to be moved around with forklifts, and was frequently transported via large cargo airplanes.

In 1984, the RAMAC 350 Disk File was designated an International Historic Landmark by The American Society of Mechanical Engineers.

[19] In 2002 at the Magnetic Disk Heritage Center, a team[20] led by Al Hoagland began restoration of an IBM 350 RAMAC in collaboration with Santa Clara University.

Seeking the desired track is also faster since, with the new design, the head will usually be somewhere in the middle of the disk, not starting on the outer edge.

The IBM 1311 Disk Storage Drive was announced on October 11, 1962, and was designed for use with several medium-scale business and scientific computers.

The 10 individual read/write heads are mounted on a common actuator within the disk drive which moves in and out hydraulically and is mechanically detented at the desired track before reading or writing occurs.

The handle is turned again to lock the disks in place and release the plastic shell, which is then removed and the drive cover closed.

Disk packs are written in these attachments in IBM's count key data variable record length format.

The 2311 has ten individual read/write (R/W) heads mounted on a common actuator which moves in and out hydraulically and is mechanically detented at the desired track before reading or writing occurred.

This created an opportunity for other manufacturers to sell plug compatible disk drives for use with IBM computers and an entire industry was born.

The drive access consisted of 20 individual R/W heads mounted on a common actuator which was moved in and out hydraulically and mechanically detented at the desired track before reading or writing occurred.

A major advance introduced with the 3330 is the use of error correction, which makes the drives more reliable and reduces costs because small imperfections in the disk surface can be tolerated.

In 1973 IBM announced double density versions (-11 models) of the 3330 product line: the 3333–11, 3330-11 and the 3336–11; the 3336-11 Disk Packs hold up to 200 MB (808x19x13,030 bytes).

Up into the early 1990s the term Winchester or Winnie was used for hard disk drives in general long after the introduction of the 3340, but is no longer in common use in most parts of the world.

The sister unit was called the IBM 3375 and used count key data architecture, which was required for OS/360 and successor operating systems.

The last models were withdrawn by IBM in May 1996 representing a production run of 15 years; a run longer than most disk drives[48] The IBM 3390 Direct Access Storage Device series was introduced November 1989, offering a maximum storage of up to 22 gigabytes in a string of multiple drives.

A single 14-inch (360 mm) oxide-coated aluminum disk spun in a plastic shell with openings for the read/write arm and two heads.

Developed at IBM's Hursley, UK, laboratory under the code name Gulliver with an initial capacity of 5 MB.

[5] Developed at IBM's Hursley, UK, laboratory under the code name Piccolo with an initial capacity of up to 65MB, it used six 8-inch disks (210 mm) and had an improved rotary actuator.

[67] Developed at the IBM Rochester, Minnesota, laboratory as the 21ED it was an 8-inch HDD with an initial capacity of 15 or 30 MB in two or four 210 mm disks.

[67] Developed at IBM Rochester, Minnesota, under the code name "Grant", it was a 70 MB ESDI full height 51⁄4-inch HDD with up to four 130 mm disks.

[67] Developed at IBM Rochester, Minnesota, under the code name "Grant-Prime", it was a full-height 51⁄2-inch HDD with a capacity of up to 115 MB on up to four 130 mm disks.

[67] Developed under the code name "Lee" at IBM Rochester, Minnesota, it was an up to 316 MB ESDI full height 51⁄4-inch HDD with up to eight 130 mm disks depending upon model.

Developed under the code name "Corsair", it was a 31⁄2-inch HDD with the height of a 51⁄2-inch half-height device (1.6-inch high) and up to 1 GB on up to 8 95 mm disks.

Developed under the code name "Allicat" at IBM Rochester, Minnesota, it was a full-height 51⁄2-inch HDD (3.25-inch high) that combined two 31⁄2-inch devices in one, with up to 2.013 GB capacity on up to 8 95 mm disks.

IBM made extensive preparations to manufacture such models and smaller form factors but cancelled all such efforts in 1985.

[7] The following table compares IBM's first HDD, the RAMAC 350, with the last three models it manufactured in each of its "Star" series of OEM HDDs.

IBM in some of its operating systems classifies HDDs and FDDs as DASDs, direct access storage devices.