History notes . . .

We Never Lost a 2314 Disk Pack

by Conrad Weisert, July 16, 2014
ŠInformation Disciplines, Inc.

NOTE: This document may be circulated or quoted from freely, as long as the copyright credit is included.


The announcement in 1964 stirred programmers's imaginations. The just-announced System/360 line from IBM would offer a new direct-access storage device, the 2314, with removable media having sufficient capacity to support on-line applications and extensive program libraries. Each disk pack would hold 25 megabytes of data, and the device contained 8 units for a total of 200 megabytes, nearly a quarter of a gigabyte of on-line accessible storage. And the ability to remove and swap the disk packs suggested virtually unlimited capacity.

Until then many organizations, even large sophisticated users, had used magnetic tape as their principal permanent storage medium. Tapes had large capacity and were fairly reliable, but file access was strictly sequential, which might require many hours of elapsed time for batch processing and ruled out most on-line applications.

Direct access storage up to then had been limited to huge fixed devices. The IBM RAMAC, resembling an oversized jukebox, contained 50 24-inch disks spinning at 1200 rpm. Observers joked that if a program should ever arrange all 1 bits on one side and all 0 bits on the opposite side, the thing would shake itself to pieces. Even then, those devices didn't offer sufficient capactity for, say, an airline reservation system or a large insurance claims processing system.

So, the big attraction of the 2314 was that it offered huge capacity in a small space. Of course "small" is relative, and today's programmers are amazed that we ever thought of a ten-pound object the size of a wedding cake as small.

When desktop computers started to take over in the 1980s, they offered very little removable storage capacity. Double-sided 5-inch diskettes were useless for most purposes. When they were replaced by 3-inch high-density ones that could hold over a megabyte of data, we saw that as a breakthrough. If you needed higher capacity you used fixed non-removable disks, which imposed messy back-up and restoration procedures.

Is smaller always better?

Today we look back upon all those devices with amused disdain. We routinely carry in our pockets solid-state storage media containing more than an entire bank of eight 2314 units, and the cost per byte has dropped by orders of magnitude.

But there's a serious downside to technological progress. Today's removable storage media are hard to keep track of and easy to mislay. On most of them there's no place to affix a sticker identifying the contents or use, so when we find one we have to put it into a computer in order to identify it. They fall out of our pockets and slip behind seat cushions. If one falls on the floor, it can be taken up by a vacuum cleaner. They risk being demagnetized by airport metal detectors. Despite their faillng prices, they're still too expensive to be given away or turned in as students' homework projects.

So, veteran computer people miss 2314 and similar removable disk packs, which were immune from such loss. We also miss 3-inch diskettes that were cheap enough to throw away. But we're glad to have and exploit the newer high-capacity removable technologies.

Last modified July 16, 2014

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