Magnetic drum acts as input/output medium for a computer. It has rotating cylinders, which are coated with a magnetizable material. The rotation rate of a drum can be much
higher than a disk as a result of a narrow cylindrical shape, and rotational delay is thus
reduced. The configuration of a drum is shown in Fig 8.8. The outer surface of the drum
is divided into a number of tracks. The top and bottom of the drum are not used for
storage, and the interior of the drum is not used for storage, so there is less capacity per
unit volume for a drum unit than there is for a disk unit. The transfer time for a sector on
a drum is determined by the rotational delay and the length of a sector. Since there is no
head movement, there is no seek time to consider. Nowadays, fixed head disks are
configured in a similar manner to drums with one head per track, but are considerably less expensive per stored bit than drums since the surfaces of platters are used rather than
the outside of a drum. The drums are nearly obsolete today and is being replaced by
fixed disks.
higher than a disk as a result of a narrow cylindrical shape, and rotational delay is thus
reduced. The configuration of a drum is shown in Fig 8.8. The outer surface of the drum
is divided into a number of tracks. The top and bottom of the drum are not used for
storage, and the interior of the drum is not used for storage, so there is less capacity per
unit volume for a drum unit than there is for a disk unit. The transfer time for a sector on
a drum is determined by the rotational delay and the length of a sector. Since there is no
head movement, there is no seek time to consider. Nowadays, fixed head disks are
configured in a similar manner to drums with one head per track, but are considerably less expensive per stored bit than drums since the surfaces of platters are used rather than
the outside of a drum. The drums are nearly obsolete today and is being replaced by
fixed disks.
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