IBM 1311

1963 IBM 1311
1st drive with 14” disks
1st drive with interchangeable disk packs enabling smaller and lower cost disk drives.
Introduced portability to disk drive memory

Why it’s important Provided removable media business model for next 12 years; broadened disk storage market; made possible switching applications on computer systems by interchanging disk packs.

Discussion The 1311 introduced the concept of removable memory via a disk drive using a “disk pack” which could be interchanged between drives; the 1316 disk pack consisted of a stack of 6 disks providing 10 magnetic surfaces for storage (top and bottom surfaces unused). The interchangeability provided “unlimited” offline storage, a function only of the number of disk packs purchased, and the time required to exchange them … a few minutes per drive. Thus a data center could convert its operation from payroll to inventory simply by switching disk packs. This technology also provided the ability to move large amounts of data from site to site (pre-internet days), which proved popular with companies needing to update multiple sites with the same database (e.g. weekly pricing for a grocery store chain). Some new businesses sprang up based on the new business model, one of which was an armored truck company which would move data around as if it ware cash. Some high security installations also used removability to take sensitive data off-line when not in use, a military officer was quoted as saying “I know my data is secure when it’s locked in my desk.” Military versions of the disk pack were available to armed services, with metal parts treated to withstand high humidity.

The disk pack was intended to be a low cost device, with an established goal of <$100 manufacturing cost. Although this was achieved (Ron Kubec managed the project),accounting policies were later revised with added overhead charges which then exceeded the cost goal.

The 2311 followed the 1311, using the identical disk pack, with a capacity increase from 2 to 7.4 megabytes. Drive design was similar, the principal difference being increased recording density. Success of the 1311/2311 also engendered lower priced “plug compatible” disk drives and non-IBM disk packs. Users found substantial savings by replacing or increasing numbers of drives with products from Memorex, CalComp, and Ampex, plus other vendors. IBM-compatible disk packs were offered by larger established firms including Memorex, 3M, CDC, and BAS and start-ups such as Caelus, an IBM spin-out. A number of hardware makers also purchased private label disk packs from established vendors, since the manufacture of disks was not their expertise. IBM’s business model was to lease both the drive and disk pack, so competitors were forced to follow suit. IBM’s timing advantage and higher pricing quickly repaid the hardware cost, while new entrants found their lower prices extended the payback, sometimes beyond the useful life of the products. Short life cycles combined with capital costs to finance drive and pack production, plus the need to refurbish leased products (without revenue) eventually drove many suppliers out of drive and disk pack business. New model disk pack drives (including non-compatible unique versions) continued being announced into the 1980's DEC RA60 was likely the last significant such product.

  • First 14 inch disk media, predecessors were 24 inch diameter and fixed disk.
  • First disk drive with exchangable and portable media
  • "Unlimited" off-line storage capability at lower cost than multiple fixed disk drives
  • Easily transportable databases offered transfer of mass storage between facilities
  • Small cabinet drive (about the size of a water cooler), significant data storage in a 10 pound disk pack

  • Allowed cross contamination between disk packs and drives, "typhoid Mary syndrome"
  • Required any disk pack to be mechanically compantible with any drive.
  • Drive cabinet could be opened while disk pack spinning, allowing entry of contaminants

Anecdotes for possible inclusion, human side of disk drives
  1. Pot Holder Disk Brake -- Bill
  2. shaft brake debris -- Bill
  3. Military burns their disk pack ... and heads too -- see George Santana
  4. Paint Additive #11, non standard usage issues -- Bill
  5. Ball Mill debris & durability -- Bill
  6. Smog collected by heads at SJC airport -- Bill
  7. CE pack erased in back of VW Bug

Additional information
IBM Archives 1311 Site
IBM San Jose, A Quarter Century Of Innovation”, David W. Kean, 1977, CHM accession number: 102687875

Provenance note: This page was originally authored by Bill Carlson; his last approved revision was version 18

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