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| From the late 1980's through 2002 the internal
or maximum media data rate of Hitachi GST hard drives increased
at about 40 per cent per year. Today's server class hard disk
drives have one of the highest internal data rates in the industry,
beyond 100 MBytes/s. This increase is the result of increasing
linear densities and disk rotation rate to 10,000 and 15,000
RPM. To moderate this data rate growth as well as control power
dissipation designers have elected to reduce disk diameter from
95 mm to 84 mm, and now to 65/70 mm. However with continued
linear density increases, it is possible that data rates will
far exceed 100 MBytes/s after the year 2004 as a subsequent
continuation of this trend. Linear density increases beyond
700 Kbits/in as well as a trend to increasing disk rotation
rate beyond 15,000 RPM are possible. The use of PRML data channels,
which Hitachi GST introduced in1990, and PRML extensions as
well as advanced ECC coding techniques have been an important
factor in allowing high internal data rates . Adopting 4096
bytes data blocks in the future to replace the existing 512
bytes standard will allow this progress in expanded linear density
to continue. |
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