defragmentation in FreeBSD 4.11

[Lowell Gilbert]

Bob Johnson <bob89 at eng.ufl.edu> writes:

> Message: 6
> Date: Thu, 28 Jul 2005 11:20:31 +0300
> From: Victor Semionov <victor at vmpbg.com>
> Subject: Re: defragmentation in FreeBSD 4.11
> To: freebsd-questions at freebsd.org
> Message-ID: <200507281120.31564.victor at vmpbg.com>
> Content-Type: text/plain;  charset="windows-1251"
> 
> 
> > > This is one of the things I find really hard to get Windows users to
> > > understand.  They just won't believe that a company like Microsoft would
> > > still be using a filesystem that needs defragmenting if it were possible
> > > to design one that didn't.  I often wonder why myself - after all, they
> > > must have put a fair amount of work into NTFS, which at least doesn't
> > > seem to get corrupted in a power failure.  Did they make a trade-off I
> > > don't understand, or is it just incompetence - or worse, a deal with
> > > disk manufacturers to sell more disk?
> > 
> 
> Microsoft used to claim that NTFS doesn't need defragmentation.  Compared to 
> MSDOSFS, that's a reasonably accurate statement, but if you push it hard 
> enough, it will still become fragmented.
> 
> > 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.