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This paper provides a comprehensive overview of digital magnetic tape subsystems that were used in the computing industry from 1953 to 1980. These subsystems were an integral part of the IBM mainframe computer systems during that period and provided numerous levels of data storage, including main memory storage, in the late 1950s and 1960s. In response to customer needs, tape subsystems enhancements were designed to be backward-compatible, allowing customers to read their older tapes on each new tape subsystem. Many key areas of tape technology are discussed in this paper, including the large number of features that were developed to make tape a viable high-speed, start-stop recording technology.
IBM computers from the 1950s used tapes similar to that used in audio recording, and IBM technology soon became the industry standard. Early IBM tape drives were large, mechanically sophisticated devices that used vacuum columns to maintain long U-shaped loops of tape. Today, modern tape systems use reels that are much smaller than those used in the early days of tape systems, and the tapes are contained within a cartridge to protect the tape and to facilitate handling. The first IBM tape drive was the IBM 726 tape drive, which was shipped to customers in 1953. This drive stored a total of 1.4 megabytes (equal to that of one floppy disk today) on a movie reel more than twelve inches in diameter.
In contrast to these early tapes, consider the May 2006 announcement in which researchers at the IBM Almaden Research Center packed data onto a test tape at a density of 6.67 billion bits per square inch. Bruce Master, senior program manager of worldwide tape storage systems at IBM, said that if products using the new IBM data recording technology hit the market in five years as expected, a standard linear tape open (LTO) tape cartridge could hold eight trillion bytes of uncompressed data.
Today, tape is still often used for the archiving of data and for data replication. Tape provides one of the technologies that help enterprises meet federal compliance regulations. On a per-gigabyte basis, tape systems are about a fifth of the cost of hard-disk-drive storage systems. According to IDC, the 2005 worldwide market for branded tape drive and tape library automation was about $4.82 billion.
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