A Bernoulli Box is a removable hard disk cartridge storage device or to put it another way, diskette drives that accommodate 10 or 20 megabyte cartridge diskettes. The two advertised and perceived uses of a Bernoulli subsystem are that it provides a single PC with a virtually unlimited amount of hard disk storage space, and functions as a backup system that generates ‘working’ copies.

This technology has been applied in a way that allows many PCs to use a single Bernoulli Box for conventional applications as well as creating access to a common hard disk storage device.

Case Study

A client had a three-terminal, 40 megabyte, Apple III/Corvus Network. They had run out of hard disk space and a consultant had recommended the purchase of an 80 Megabyte hard disk as a solution to its problems. Since the system was old, unreliable and could not run IBM based software, a Requirements Analysis was performed to determine the cost to address its data processing needs in an MS-DOS environment.

Interviews with staff and management revealed that this firm performed three data processing functions:

• Word Processing
• Electronic Spreadsheet
• Write-up Work

All of these functions needed to be performed by three support staff at separate locations. The word processing and spreadsheet functions did not require the sharing of data. However, account write-up work was to be expanded, and management wanted each staff person to be able to perform write-up work on any of their accounts.

Initially, a Local Area Network (LAN) was explored. However, the estimated cost of the network exceeded the amount of the client’s budget for a system. So the problem posed by this engagement became: How can the three users have access to the same data source without incurring the cost of the Local Area Network?

Further inquiries regarding the way in which each user needed to share the common data source revealed the following characteristics:

• No user needed to access the same account at the same time.
• The deadlines for the accounts were at different times during the month.
• Because of the many staff duties, the timing of access to the shared data source was flexible.

With this information, the requirement of sharing a common data source took on a new look. The shared data source did not have to be available to multiple users at the same time, but only distinct single users at different times.
The Bernoulli Box, in its traditional role, met all the needs of this client in a single user mode.

Increased Hard Disk Space

The client was expanding his account base which would increase hard disk requirements substantially. With the Bernoulli Box, the client would have infinite hard disk capacity and could very economically increase hard disk space by purchasing additional cartridges.

Data Security, Backup

The Bernoulli Box offered backup and disk storage features that were particularly attractive to this client:

• The ability to store systems of different accounts on separate cartridges was a desired security feature.
• If one cartridge went bad, it only affected one account. This would not be the case on a conventional hard disk.
• The ability to have a ‘working copy’ as a backup was attractive to the client because of its immediate usability.

The fact that there were two cartridge diskette drives provided additional security. If one of the cartridge diskette drives became damaged, the other drive could be used while the damaged one was out for repair. This would not be possible with a conventional hard disk. The only requirement not addressed by the use of a Bernoulli Box was the access by multiple users. This requirement was met by attaching the Bernoulli Box to a three-station switching device, purchasing Bernoulli Box control cards for each of the three computers, and connecting the new computers to the switching device. With this configuration, each one of the PCs could have access to the Bernoulli Box – but only one at a time. A user desiring access only needed to switch their channel, insert a hard disk cartridge, and type “D:”

The client was pleased with this alternative because it addressed all of its data sharing needs without excessive additional cost.

A Local Area Network is preferable when the sharing of a common data source is needed. But in a situation where the cost of a network is prohibitive and the sharing of requirements are limited, the un-traditional application of removable hard disk technology provided the client with an acceptable alternative.

The microcomputer industry is changing at a phenomenal rate. Advancements in technology are constantly providing us with new alternatives to managing client’s data processing needs. Sometimes, the correct solution for our client lies not in that new technology, but rather in proven technology applied in a unique way.

Published in The CPA Journal, March 1988, pp. 68-69.