I found this excellent narrative at Tiger Direct of Canada. This is open information I just wanted to give credit for the method used by Tiger Direct to present this sometimes difficult to understand subject
- The way size is calculated and
displayed.
- Any "Partitions" on the disk will
change the total in a specific partition.
- Hidden files and folders decrease
available space.
- Compression increases the apparent
size, but not the physical size.
- Drives larger than the OS or Drivers
natively supports.
First, the definition of a megabytes
(or gigabytes) is a unit of data storage capacity measured in 1,048,576
bytes (or 1024KB). The larger the numbers, the more apparent the size
difference will be when listing the size as megabytes (or gigabytes) versus
bytes. Actually, both numbers are correct. The noticeable difference is due
to the 1024KB definition of a megabyte. This is why a 95.3GB hard drive can
also be listed as having 102 billion bytes of total space. Just think
of it as "round off"
In the screen shot at right:
The first number is the total number of bytes,
the second number is based on the number of megabytes or gigabytes.
Second, some computers have a
non-DOS hard drive partition that is used for features such as Save to Disk,
Hibernation, or Recovery. This partition is not normally reported by the
operating system, although it can be viewed using a disk partition utility.
This is very common on desktops and laptops.
NOTE:
Partition information will be created or
formatted automatically during initial system setup and a system recovery.
Third, by default, all system files
are hidden and cannot be seen. This may adversely affect the reporting of
available hard drive space. You can set your Folder Options so you view
system and hidden files and folders, but do be careful as changes to system
files can adversely affect your system.
Fourth, if you turn on Compression
for a drive, it will increase reported free space and used space, but since
compression is based upon the actual contents, this number is not fixed, but
will change as files are added or changed.
Fifth, older operating systems did
not support some of today's larger drives, so the total space reported may
be much smaller than the drive specifications.
It is also worth noting that bad sectors
are corrected by your operating system and can change the total drive space,
free space, or used space as well.
So as long as a drive is reporting a value
approximately close to the specification value, you can be comfortable that
you received the right drive and that you are getting to correct data
storage. Of course, tuning of your drive's partitions and options can
yield optimal values, but this is not something for the average user to
explore.
Additional information on this topic can be found here:
http://en.wikipedia.org/wiki/Hard_disk_drivehttp://simple.wikipedia.org/wiki/Hard_disk
