6.4. SAN Backup Media
6.4.1. Past Backup Media
If we ignore that period of time when punch cards and paper tape were used as backup media, tape has always been the medium of choice for backup. It is dense and relatively inexpensive.
As described in Chapter 2, tape emerged in the 1950s and 1960s as a 9-track, 1200’ (or shorter!) open reel medium on 10’ (or smaller!) reels. It had a density of 800 bits per inch. The length expanded to 2400’ and density increased to 6250 BPI. Through the 1970s, open-reel tape was the only serious medium for backup, and indeed the residence of many batch-processed master files and transaction files.
The operator at an IBM mainframe shop would be known as either the “console commander” or the “I/O hanger,” depending ...