1.3 The Signs of a SAN

2.1 How Did We Get to Networking Storage Anyway?

Remember your very first computer class where the teacher talked about the three basic elements of a computer (Figure 2-1)?

Figure 2-1. Basic Elements of a Computer

Then the teacher said there were three functions to the processing element. That processing consisted of the:

• control function

• arithmetic logic unit (ALU)

• memory

This is where it all began ”with the core memory, the internal storage. It was also called short-term storage. This short- term storage, also known as volatile storage, was used by a program during the processing of instructions, and then it was made available for the next program to use.

One of us (Barry) has an early memory of such processing:

At the risk of sounding like I grew up with mastodons, I remember the early 1960s, when my high school math class was taken to Control Data Corporation in Sacramento, CA, to do some programming. At the console keyboard (electric typewriter, really), each of us took a turn entering numeric op codes and physical addresses from hand-written notes. It was a thrill to watch the program run. Of course, when my turn was done, my program was cleared out so the next one could be entered.

Long-term storage was simply the paper the report was printed on. All the data from the program had to be printed out because there was no place else to store it.

As you may know, paper tape was once a fashionable place to store the program, and data too. After all, it had respectable roots with the Teletype machine as a medium for pre-coding and duplicating messages. Further, it did not go out of fashion as long ago as people may think. In 1984, for example, as PCs were making their appearance in business, paper tape was still the medium of choice for entering APT (Automatic Programmed Tools) instructions into CAD/CAM machine tools.

A significant storage medium was the punch card, or Hollerith card (eventually known universally as the IBM card, to the dismay of Burroughs and Univac). Cards had been storing data since the 1890 census. In 1911, Charles Flint effected the merger of Hollerith s Tabulating Machine Co. with the Computing Scale Co. of America and the International Time Recording Co., giving us C-T-R, which was to become IBM.

For decades, data stored on cards was processed on tabulating ( tab ) equipment, not computers. When technology evolved to a point where there was such a thing as a stored program computer, cards could be used to store programs, input data, or output data.

As technology developed, long-term, external storage became available in the form of magnetic tapes and disks. However, the keypunch department was still an important part of the data center as late as the late 1970s.