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From: Bob Johnson <bob89@eng.ufl.edu>
Organization: UF College of Engineering
To: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org>
Date: Thu, 28 Jul 2005 15:46:55 -0400
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Cc: Victor Semionov <victor@vmpbg.com>, freebsd-questions@freebsd.org
Subject: Re: defragmentation in FreeBSD 4.11
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On Thursday 28 July 2005 03:07 pm, Lowell Gilbert wrote:
> Bob Johnson <bob89@eng.ufl.edu> writes:
> > From: Victor Semionov <victor@vmpbg.com>
[...]
> > > Why is it unnecessary to defragment UFS?
> >
> > In normal use, files never become fragmented enough to affect
> > performance.  In a (loose) sense, files are intentionally fragmented in a
> > controlled way so that fragmentation doesn't cause problems.  If you run
> > fsck on a partition, you will typically see fragmentation levels of less
> > than one percent.
>
> Careful, there; "fragmentation" on a UFS is measuring a completely
> different thing than the same term applied to a Microsoft filesystem.
> For UFS, it refers to non-contiguous free blocks (fragments,
> actually), as opposed to the Microsoft terminology, where it refers to
> non-contiguous blocks within the same file.
>
> Everything you are saying is correct, but it will confuse people who
> don't realize the difference.

Yeah, I was trying to keep a long response from getting even longer.  And I 
didn't really know what fsck is measuring when it reports fragmentation, so I 
got lazy and glossed over it instead of digging up the information.

Thanks for keeping me honest,

- Bob