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Initially, magnetic tape for data storage was wound on large (10.5 in/26.67c cm) reels. This defacto standard for large computer systems persisted through the late 1980s. Tape cartridges and cassettes were available as early as the mid 1970s and were frequently used with small computer systems. With the introduction of the IBM 3480 cartridge in 1984, large computer systems started to move away from open reel tapes and towards cartridges.
Early half-inch tape had 7 parallel tracks of data along the length of the tape allowing, six-bit characters plus one bit of parity written across the tape. This was known as 7-track tape. With the introduction of the IBM System 360 mainframe, 9 track tapes were developed to support the new 8-bit characters that it used. Effective recording density increased over time. Common 7-track densities started at 200, then 556, and finally 800 cpi and 9-track tapes had densities of 800, 1600, and 6250 cpi. This translates into about 5 MB to 140 MB per standard length (2400o ft) reel of tape. End of file was designated by a tape mark and end of tape by two tape marks.
LINCtape, and its derivative, DECtape, were variations on this round tape. They were essentially a personal storage medium. The tape was ¾ inch wide and featured a fixed formatting track which, unlike standard tape, made it feasible to read and rewrite blocks repeatedly in place. LINCtapes and DECtapes had similar capacity and data transfer rate to the diskettes that displaced them, but their seek times were on the order of thirty seconds to a minute.IRG of Magnetic tape is 0.75d inch
Tapes must be encrypted if you send them offsite. There are a number of options, such as replicating deduplicated backups, continuous data protection (CDP), and near-CDP, but suffice it to say that the three rules of encryption are key management, key management, and key management. Lose your keys and lose your data.
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