Acomdata PDHD1000USE-72, User Manual

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Q: Why is the capacity of my Drive, as shown on my computer,
lower than the Drive’s stated capacity?
A: The difference is mostly due to the way Windows and Mac operat-
ing systems measure storage capacity, as compared to the method
used by hard drive manufacturers. Hard drive manufacturers have
always used the decimal (base 10) method, where 1GB = 1,000 MB
= 1,000,000 KB = 1,000,000,000 bytes. Operating systems use the
binary (base ) method, where 1GB = 1,0 MB = 1,0,5 KB =
1,0,1, bytes. For example, a 10 GB hard drive partition will
mount as approximately a 111. GB volume on your computer's OS.
The reason the number will be approximate is because the actual
number of available bytes of storage on a 10 GB hard drive will not
be exactly 10,000,000,000. It is actually a bit more than that. We
just round down the figure to 10 GB for simplicity's sake.
Hard drive manufacturers use the decimal method because it is
simpler and less confusing to most consumers. Manufacturers of
operating systems do not need to concern themselves with this
issue, so they typically use the more traditional binary method.