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January 17, 2006, 10:51 am
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measurements. I want to compare the sound levels produced by Samsung
Spinpoints and Western Digital Caviar (amongst other things, like failure
rates and statistics).
TomsHardware is good for reviews, but I couldn't see any info on noise
levels and MTBF (failure rates?).
Re: Sounds reviews
"Idle Noise - The sound pressure emitted from a drive measured at a
distance of 3 millimeters. The close-field measurement allows for
increased resolution between drive sound pressures and eliminates
interactions from outside environmental noise. Note that while the
measurement is an A-weighted decibel score that weighs frequencies in
proportion to human ear sensitivity, a low score does not necessarily
predict whether or not a drive will exhibit a high-pitch whine that
some may find intrusive. Conversely, a high score does not necessarily
indicate that the drive exhibits an intrusive noise profile."
The numbers are only suitable for comparison between drives measured
in the same testbed. You cannot compare the values measured with the
manufacturer's claims, neither can you compare one manufacturer's numbers
to another, due to the differences in how the measurements were done.
In other words, while seeing that chart of numbers is comforting, it
doesn't guarantee that the drive you buy is not annoying.
Published failure rates are "by calculation" and are computed when the
product is first introduced. They are based on field data, in a limited
sense. For example, if fluid bearings have been around for X years, then
the reliability of the bearing itself can be accounted for with real
field data. But the datasheet value is not based on field returns of
the finished whole product, and the field return data is the best
indicator of what the true failure rate might be. In other words, if
you work in the RMA department at Newegg, you probably know exactly
what the reliability is for the various brands and models of drives.
A calculation in a datasheet is not nearly the same thing - the datasheet
calculation is more for the purpose of a large company figuring out how
many spare drives to stock for repairs per year (from MTBF, you can work
out % failures per year). The calculation should not be used to
determine that "my drive will last for exactly 114 years" - the
calculation is statistical in nature.