Return to BSD News archive
Newsgroups: comp.os.386bsd.questions
Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!haven.umd.edu!news.umbc.edu!europa.eng.gtefsd.com!howland.reston.ans.net!xlink.net!math.fu-berlin.de!zib-berlin.de!informatik.tu-muenchen.de!wiserner
From: wiserner@Informatik.TU-Muenchen.DE (Bernd Wiserner)
Subject: Re: [NetBSD 0.9] filesystem weirdness?
References: <Added.EgzA4=200UdbQeJE5j@andrew.cmu.edu> <2dilh7$rf0@homer.cs.mcgill.ca>
Sender: news@Informatik.TU-Muenchen.DE (USENET Newssystem)
Organization: Technische Universitaet Muenchen, Germany
Date: Wed, 1 Dec 1993 22:35:16 GMT
Message-ID: <1993Dec1.223516.14726@Informatik.TU-Muenchen.DE>
Lines: 49
In article <2dilh7$rf0@homer.cs.mcgill.ca> storm@cs.mcgill.ca (Marc WANDSCHNEIDER) writes:
>In article <Added.EgzA4=200UdbQeJE5j@andrew.cmu.edu>,
> <Todd.Williamson@IUS4.IUS.CS.CMU.EDU> wrote:
>>
>>I'm not sure whether I did something wrong, or if this is a "feature,"
>>but I want it fixed:
>
>>
>>Upon cursory examination, it seems like 10% of my filesystems is
>>"reserved," and I have to be root in order to write in the last 10%.
>
> This is INHERENT to the way Berkeley Fast File System works. It
> reservees 10% for performance improving scratch space and other
> things. Using this 10MB of disk space causes serious
> performance degradation.
Hmm it depends on how you use your filesystem ...
I did some 'benchmarks' ( untar a distribution , delete some dirs,copy some others ,
compile a kernel....
As far as the benchmarks were somehow 'representative' this is what they told me:
10% minfree = 100%
5% minfree = 104-106% ( 4-6 % slower )
3% minfree = 107-111% ( 7-11%slower)
1% minfree = 115-125% ( 15-25% slower. )
0% minfree = 140-200% ( 40-100%slower.)
So it isn't such a performance hit. ( Ok 0% or 1% is a little bit drastic ... :-)
Theese values are measured with a 500 Mb filesystem. If you have a smaller partition
things will be worse.
Another question is : How much 'costs' your time ?! How long do you have to wait
untill it pays to spend another 100$ for 100Mb of disk.
And still another question is this : If you can't sleep because you have
100 Mb on you disk doing nothing it would be better to decrease minfree before you
go gaga.
>
>>So, how to I fix this?
boot singleuser . ( The partition which will be changed shouldn't be
mounted.)
type tunefs -m 5 /dev/{diskdevice}
>
> Toodlepip!
> Marc 'em.
>
>--
>-----------------------------------------------------------------------------
>Marc Wandschneider Seattle, WA
>Barney the Dinosaur sings! You faint... Barney sings! Barney sings! --More--
>You Die... --More--
B.Wiserner