tar: Media
1
1 9 Tapes and Other Archive Media
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1 _(This message will disappear, once this node revised.)_
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1 A few special cases about tape handling warrant more detailed
1 description. These special cases are discussed below.
1
1 Many complexities surround the use of 'tar' on tape drives. Since
1 the creation and manipulation of archives located on magnetic tape was
1 the original purpose of 'tar', it contains many features making such
1 manipulation easier.
1
1 Archives are usually written on dismountable media--tape cartridges,
1 mag tapes, or floppy disks.
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1 The amount of data a tape or disk holds depends not only on its size,
1 but also on how it is formatted. A 2400 foot long reel of mag tape
1 holds 40 megabytes of data when formatted at 1600 bits per inch. The
1 physically smaller EXABYTE tape cartridge holds 2.3 gigabytes.
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1 Magnetic media are re-usable--once the archive on a tape is no longer
1 needed, the archive can be erased and the tape or disk used over. Media
1 quality does deteriorate with use, however. Most tapes or disks should
1 be discarded when they begin to produce data errors. EXABYTE tape
1 cartridges should be discarded when they generate an "error count"
1 (number of non-usable bits) of more than 10k.
1
1 Magnetic media are written and erased using magnetic fields, and
1 should be protected from such fields to avoid damage to stored data.
1 Sticking a floppy disk to a filing cabinet using a magnet is probably
1 not a good idea.
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