Date: Tue, 19 Sep 2006 13:13:55 -0400 From: Jerry McAllister <jerrymc@msu.edu> To: Wayne Sierke <ws@au.dyndns.ws> Cc: freebsd-questions@freebsd.org Subject: Re: Reducing reserved space on large filesystems Message-ID: <20060919171355.GB18826@gizmo.acns.msu.edu> In-Reply-To: <1158683484.851.166.camel@ovirt.dyndns.ws> References: <1158683484.851.166.camel@ovirt.dyndns.ws>
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On Wed, Sep 20, 2006 at 02:01:23AM +0930, Wayne Sierke wrote: > I was very interested to read the following written by Matthew Seaman in > 2004. > http://lists.freebsd.org/pipermail/freebsd-questions/2004-January/033754.html > > The parameters given to newfs(8) don't depend on the size of the > filesystem, so much as the size of the files you intend to store > within it, and the sort of directory structure you want to use > (ie. how many files per directory) Many of the tunables in newfs(8) to > do with the details of disk geometry don't make sense with modern > drives and should be ignored. > > You should try running 'newfs -N' with various values for the '-g' > average file size and '-h' average numbers of files per directory > parameters to see what sort of numbers it spits out. You don't have > to be too accurate with those file size and files per directory > estimates -- order of magnitude is generally good enough. Unless > you're going to be storing exceptionally large files (say, typical > size 20Mb) or you want to have directories with 5,000 or more files in > them, then just using the newfs(8) default values will work very well. > > One thing you can do for any file system over about 256Mb is drop the > free space reserve ('-m' option in newfs(8), or it can be modified in > an existing filesystem using tunefs(8)). 1% is more than adequate if > you're creating a multi-gigabyte filesystem. > > I'm especially interested in the comment about the 'free space reserve' > which flies in the face of everything I can recall ever reading that has > always mirrored the warnings in tuning(7) and tunefs(8) about the perils > of reducing the reserved space below the default. However I didn't see > any reply to Matthew's email to repudiate his statements. > > What are people's experiences in the field? Are the cautions now much > less relevant with modern hard-drive capacities and performance? The free space reserve is most important on file systems that root will need to write to in order to keep the system itself going. In places that you put data that is fairly controlled, you can get away with having a very small free space reserve, though some is probably a good idea. Those tend to be the huge file systems where having 8% or 10% reserved makes a big difference in the amount of disk being tied up. ////jerry > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org"
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