Date: Mon, 7 Jun 1999 12:04:46 -0500 (CDT) From: Kevin Day <toasty@home.dragondata.com> To: joe@nall.com (Joe Nall) Cc: freebsd-isp@FreeBSD.ORG Subject: Re: Full filesystem Message-ID: <199906071704.MAA09057@home.dragondata.com> In-Reply-To: <375BFAAE.CCC65835@nall.com> from Joe Nall at "Jun 7, 1999 12: 0:30 pm"
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> spork wrote:
> >
> > Hi,
> >
> > We're running a news server that does a "rolling expire", so it is capable
> > of keeping the drives 99% full (31GB) 24/7. We have two 34G ccd arrays,
> > so even bumping down one percent is kind of a waste of space. Since newfs
> > gives a buffer zone for safety (you can fill the fs to 105% or so), I want
> > to keep usage up above the warning zone.
> I'm not an expert on this filesystem, but on other filesystems that
> extra 5-10% is used by the filesystem to minimize fragmentation. On
> HP-UX there is a definite performance impact when this is made too
> small. Can a filesystem guru clue us in on the right rule of thumb? Is
> it 10% or is there a particular total size (e.g. 500mb) above which the
> extra space is wasted? I'm going to do some big raids this summer and 5%
> of 100+GB starts to add up.
>
To quote 'tunefs'
-m minfree
This value specifies the percentage of space held back from nor-
mal users; the minimum free space threshold. The default value
used is 8%. This value can be set to zero, however up to a fac-
tor of three in throughput will be lost over the performance ob-
tained at a 10% threshold. Settings of 5% and less force space
optimization to always be used which will greatly increase the
overhead for file writes. Note that if the value is raised above
the current usage level, users will be unable to allocate files
until enough files have been deleted to get under the higher
threshold.
So, keep that in mind. :)
Kevin
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