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SubjectDetermining maximum partition size on a hard disk
I am trying to calculate the maximum size a partition can be on a hard
drive and I ran into some problems I don't fully understand.

First I found that the maximum size of the drive Linux reports is not
the maximum size I get when I calculate it from the drives geometry.
Secondly, the total drive space reported by linux is not the amount
available for the maximum partition.

For example, I have a 4.3Gb disk. The drives geometry is 525 cylinders,
255 heads and 63 sectors (525 * 255 * 63 * 512 = 4318272000 or

This is an IDE disk so I found in /proc/ide/hdx/capacity a block size
8439184, which when divided by 2048 is 4120.7, ~200Mb less than what I
calculated as the disk size.

Finally, using a program such as fdisk or sfdisk I create a partition
manually to be the maximum amount allowed, which turns out to be 4217041
blocks, or, when divided by 1024 is 4118.2.

I assume that the difference between the maximum size that linux reports
and the maximum partition size is due to linux leaving room for a MBR
and such. If so how do I go about calculating this? Also why does the
size of the drive I calculate out by using the drives geometry differ so
much from the amount Linux reports? I thought maybe Linux set 1MB=1000k
but that doesn't seem to case.

Any information or a push in the right direction would be appreciated,

-Nick DeClario
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