Preservation of Historical Records (1986) / Chapter Skim
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6. Magnetic Recording Media
6. Magnetic Recording Media
Pages 61-70
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From page 61... ...
and accorded careful mechanical handling, is likely to remain usable for more than 20 years. The period of 10 to 20 years is of particular significance for all machinereadable records because it is also the useful life expectancy of the hardware itself.
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From page 62... ...
. DEFINITIONS In machine-readable records i.e., magnetic computer, audio, and video tape, magnetic and optical disks, and phonograph records it is understood that the recorded information can be usefully recovered only by converting it to a human-readable form such as paper text, a photograph, or a video terminal display.
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From page 63... ...
Because of the relatively high cost of storing data on rigid disks ( 10-3 cents per bit versus 10-6 cents per bit on taped, rigid disks are rarely considered for archival applications and, therefore, will not be discussed further. An additional factor against its archival use is the fact that the majority of today's large hard disk files "Winchester drivesJ cannot be physically separated from the head-disk assembly tHDAJ, a sealed unit.
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From page 64... ...
These Curie temperatures are so far above the normal archival storage temperatures that no difficulty is anticipated. Other magnetic effects of concern include the print-through phenomenon, in which the magnetic fields from one layer of written tape can slightly magnetize the particles in the adjacent layers on the reel.
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From page 65... ...
If all archival tapes are carefully rewound before being mounted on the computer tape transport, then very long storage periods are satisfactory. Indeed, many large computer tape archives do not include periodic rewinding in their tape maintenance programs {M.
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From page 66... ...
Offsetting this serious problem are, of course, some potentially attractive reasons for using digital recording techniques; compatibility with the computer environment and the ability to perform perfect error detection and correction are prime examples. Given the proper operating system for reading out the digital data, a further requirement arises.
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From page 67... ...
MAGNETIC RECORDING MEDIA 67 Contro~e3-environment tape storage area. Archival care of magnetic recor~ingme~a requires attention to come-ons of temperature and humi~tyas well as carefu~peno~c rewinding.
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From page 68... ...
2. Operation of short-term magnetic tape archives in accordance with the recommended storage practice detailed by Geller (1983)
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From page 69... ...
National Bureau of Standards, NBSIR 84-2988, December. See also Kinetics of hydrolytic aging of polyester urethane elastomers, Macromolecules, 13:248-252 {1980~; Hydrolytic degradation of polyester polyurethanes containing carbodiimides, Macromolecules, 15:453-485 jl982J; Equilibrium acid concentrations in hydrolyzed polyesters and polyester-polyurethane elastomers, J
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From page 70... ...
Optical disk a recent development in data storage technology. The magniped view shows digitized data encoded on the disk.
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