Date: Mon, 07 Jun 1999 17:02:44 -0500 From: Joe Nall <joe@nall.com> Cc: freebsd-isp@FreeBSD.ORG Subject: Re: Full filesystem Message-ID: <375C4184.3648AA39@nall.com> References: <199906071704.MAA09057@home.dragondata.com>
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Kevin Day wrote: > > > 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. That is not really what I was looking for. To reword the question: Is there some file system reserve above which the percentage based mechanism just wastes disk space? Is there is a measurable difference in performance between a 50GB file system with a 2.6GB reserve and a 5GB reserve? Does file size distribution impact reserve requirements? Cheers, Joe To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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