Thread: Support FAT32 is a waste of space
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Old May 23rd, 2011, 08:34 AM   #26 (permalink)
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Originally Posted by XplosiV View Post
Um, seriously, yes, because formatting the drive creates your Fat & MBR and this is why the 'usable space' of a drive is always lower. An 80gb drive only gives you 76.x gb because the fat & mbr need to use space.

Your probably thinking that of the 'usable space' you probably want to make best use of it with the smallest sector size possible. This would be on ntfs 512 bytes so the most any one file will waste is 511 bytes and this will also add up.

This is why the 'space on disk' is always larger than the stated used space, no matter what format the dive is using.
That's totally wrong. The MBR takes up 512 bytes. It's tiny. The rest of the FAT32 overhead would be a couple of megabytes at most (in an average filesystem). In rare exceptions (where a partition contains thousands of files smaller than the cluster size), the overhead might grow to a couple of hundred megabytes. It would certainly never even come close to gigabytes of space.

The reason that drives advertised as 80GB only have ~74.5GB is because drive manufacturers use a different unit of measurement to operating systems:
  • When a drive manufacturer advertises an 80GB drive, they're saying it has 80 * 10 to the power of 9 bytes, which is 80,000,000,000
  • When you plug that drive into Windows, the OS measures how many gibibytes it has. A gibibyte is 2 to the power of 30 bytes, or 1,073,741,824 bytes.

So Windows tells you that the drive has 74.5 gibibytes which is the same as 80,000,000,000 bytes. It's absolutely nothing to do with the format of the drive
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