The IBM 2321 Data Cell Drive

(See some corrections and clarfications below.)
The IBM 2321 Data Cell Drive

Early-to-mid 1960s. The Data Cell was IBM's first direct-access mass storage device. The design team was managed by IBM's Alan F. Shugart, who also was involved in the design of the first modern hard disk drive with air-bearing heads and later went on to found Shugart Associates in 1973 (which pioneered the floppy diskette) and Seagate Technology in 1979. (Contrary to the rumor that the Data Cell was designed as a thesis project by an MIT engineering student whose object was a storage system using every known technology... hydraulics, pneumatics, magnetics, springs, optics, ....) The 2321 housed up to ten removable and interchangeable data cells. Each data cell contained 200 magnetic strips, which were the basic recording media. The total storage capacity was 400 million bytes or 800 million decimal digits. Up to eight 2321s could be attached to the IBM 2841 control unit, allowing an overall capacity of over 3GB. Reportedly the Data Cell required 23 liters of motor oil.

Average access times for selection of a strip range from 175 to 600 milliseconds; average rotational delay one a strip is on the drum is 25 milliseconds; access time to another cylinder averages 95 milliseconds.

Photo

A Data Cell cartridge (foreground); the Data Cell cartridge carousel (background). Columbia's Data Cell was retired after relatively brief service, due to dependability problems; the weak point was reinsertion of the tape strip into its clip in the Data Cell cartridge after use.

Photos: IBM [32].

Here is an illustration of Data Cell, subcell, and strip hierarchy:
Photo
Photo: Introduction to IBM Data Processing Systems, IBM Textbook C20-1684, 1968.


Photo: Frank da Cruz, July 2010.
And here on the left are some magnetic media of the 1960s, 70s and 80s, a Data Cell strip is in the plastic presentation case shown at bottom. Click to enlarge, or CLICK HERE for large high-resolution view.


The following is from Peter Kaiser, who was in the Computer Center's Systems Group during the Data Cell's tenure:

I feel you've given rather short shrift to the description of the 2321 Data Cell drive, which made such a distinct contribution to the ambient noise of the ASP-era machine room. The machine room was noisy, though after working there for a while you'd become used to it, like the ticking of a clock. The waterflow regulator and gauges were swishing, printers would be clacking and hammering, tape drives whirring and clicking, disk drives humming and making head movement sounds, and in the background (literally -- it was at the back of the room) was the distinctive THUM-SLAM-KERCHUNK-WHISH of the data cell as the cells rotated into position and were locked home, and a magnetic strip was selected and flew around the read-write drum. All of this noise contributes to one of my most cherished memories.


From Tom Gardner, Los Altos CA, long-time storage industry veteran and a member of the Computer History Museum's Storage Special Interest Group, July 2010:

FWIW, I was updating the Wikipedia article on the 2321 which appears to be highly derived from the IBM 2321 Data Cell article at the Columbia computing history site. I noted a few errors and then checked with some colleagues who were far more familiar with the 2321 and came up with the following suggested corrections.

  1. It is not accurate to say that Al Shugart "designed" either the 2321 or the first modern disk drive with flying heads. He for a period of time a program manager on each those projects (one of several such managers over time).

    One bio describes this portion of his career as: "He worked as a manager of a variety of programs including IBM's 2321 data cell drive, and was instrumental in the development of the world's first disk drive, the Advanced Disk File, which became the IBM 1301." see:

    http://www.computerhistory.org/events/lectures/shugart_09052002/shugart/

    FWIW, with regard to the 2321 it was conceived as the VLCM in the late 1950s, managed by Don Johnson. In 1961 it was renamed MARS under Pete Lazarus and then in 1963 it became the 2321 under Al Shugart, but it didn't go into production until later and then under Gerry Harries. I believe Shugart was promoted to RAMP manager in 1964.

    Probably substituting the word "managed" for "designed" is sufficient, but you might consider dropping the whole Shugart thing (Ed. - The original wording was modified).

  2. The hydraulic fluid was not motor oil; it was DTE light, a very light bodied oil not unlike 3-In-1 oil. It was pressurized at 1500psi and despite a lot of folklore about oil leaks, they were very very rare. The oil sump held 5 gallons (19 liters).

  3. Some of the photos are not of actual 2321 hardware,
    • The top photo is probably a wooden mockup, perhaps taken for announcement literature. There are a number of better photos on the web so it you don't have a photo of the 2321 actually installed at Columbia u might want to pick up one of those photos. In particular see:

      http://www.computer-history.info/Page4.dir/pages/Photostore.dir/images/Picture.1.jpg

    • The middle photo is an A Test version of the MARs prototype of the 2321 which never left IBM San José. In this photo a Markite pot is above the rotating cell array, driven by an open shaft, which is in front of the strip r/w housing. The later design, including later test models and all pre-production and production versions had the Markite pot out of sight at the bottom of the rotating bin array. This later design allowed the drum drive mechanism to be hinged so that access to the strip selection mechanism could be easily obtained. You might want to note this.

    Sorry to be so picky, but I think it is important to get the facts correct, particularly since as you can see your site is the picked up by other sites such as Wikipedia.

(Ed. - Thanks, picky is good.)


Frank da Cruz / fdc@columbia.edu / Columbia University Computing History / Jan 2001 / Updated 7 July 2010