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Date:      Mon, 26 Aug 2002 18:04:42 -0400
From:      Chris Ptacek <cptacek@sitaranetworks.com>
To:        "'Giorgos Keramidas'" <keramida@ceid.upatras.gr>, Chris Ptacek <cptacek@sitaranetworks.com>
Cc:        "'David Schultz'" <dschultz@uclink.Berkeley.EDU>, Carlos Carnero <zopewiz@yahoo.com>, freebsd-questions@FreeBSD.ORG
Subject:   RE: optimization changed from TIME to SPACE ?!
Message-ID:  <31269226357BD211979E00A0C9866DAB02BB998C@rios.sitaranetworks.com>

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OK, I am still trying to get a testbed setup to 
reproduce the issue.  Once I do I am going to try
setting the block size to 4096 and the fragment
size to 512 (1:8 ratio) and minsize to 10%.  To 
do this I believe I just:
umount partition
newfs -b 4096 -f 512 -m 10 /dev/wd0s1e

Is this correct, or do I need to go through and 
delete and relabel, etc?

  - Chris

> -----Original Message-----
> From: Giorgos Keramidas [mailto:keramida@ceid.upatras.gr]
> Sent: Monday, August 26, 2002 2:00 PM
> To: Chris Ptacek
> Cc: 'David Schultz'; Carlos Carnero; freebsd-questions@FreeBSD.ORG
> Subject: Re: optimization changed from TIME to SPACE ?!
> 
> 
> On 2002-08-26 15:02 +0000, Chris Ptacek wrote:
> > I had a few questions...  What actually causes the fragmentation to
> > occur?  I have tried just copying a small file over and over and
> > this results in no fragmentation.  This leads me to believe that the
> > fragmentation is a result of simultainious open files or at least
> > different file sizes.
> 
> The way that the FreeBSD filesystem organises data on disk.  This
> "fragmentation" is not the same as fragmentation on a DOS partition,
> if this is what had you confused.
> 
> > Also it seems that when we switch to SPACE optimizaiton is based on
> > the % fragmentation based on the minfree setting.  Can I change the
> > minfree for the filesystem (I have a dedicated cache partition) to
> > like 27% (8 is default) so that I am much less likely to hit the
> > SPACE case?
> 
> Then the SPACE optimization will start when 3 times more space is
> taken by fragments.  But this is going to reserve 27% of the disk
> space for the superuser and block allocation routines.  This is too
> much disk space to reserve :/
> 
> A better solution is probably to format the partition with a fragment
> size equal to the block size as someone mentioned.  I haven't tried
> this though and I can't say how much it affects performance and why.
> 
> -- 
> FreeBSD: The Power to Serve <> http://www.FreeBSD.org
> FreeBSD 5.0-CURRENT #0: Wed Aug 21 22:08:19 EEST 2002
> 

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