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Date: Mon, 03 Nov 2003 10:51:59 +0100
From: Alexander Marx <mad-ml@madness.at>
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To: Odhiambo Washington <wash@wananchi.com>
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cc: freebsd-questions@freebsd.org
Subject: Re: How does FreeBSD calculate disk sizes
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Odhiambo Washington wrote:
> Hello users,
> 
> I have a disk which is actually 72GB. 2GB has been used as swap while
> the rest was given to /.
> 
> Can someone explain to me what I could be missing here, because what
> I am seeing isn't what I expect. Perhaps it's just right while I am
> the dumb one. Why isn't the whole size reported?
[...]

first of all, a "72GB harddisk" isn't actually a 72GB harddisk; this might
sound funny, but harddisk manufacturers are engineering people and they
are usually thinking in terms of 1000s
(see http://www.seagate.com/support/kb/disc/bytes.html)

so your disk actually only holds 72000000000 bytes (~69GB) ...
which is perfectly consistent with your fdisk output.

further, reading tunefs(8) you will find, that per default your filesystem
reserves some space (8%) for root ...

: -m minfree
:             Specify the percentage of space held back from normal users; the
:             minimum free space threshold.  The default value used is 8%.


.. subtracting 8% from the remaining 69GB roughly gives 64GB.

so your disk is just fine.

regards,
alex.