Date: Sun, 30 Nov 2008 10:43:49 -0500 From: Sahil Tandon <sahil@tandon.net> To: freebsd-questions@freebsd.org Subject: Re: does not understand "df -H" Message-ID: <20081130154348.GB49413@shepherd> In-Reply-To: <f84c38580811300540h6c18494fod7d4bebeddb4287b@mail.gmail.com> References: <f84c38580811300540h6c18494fod7d4bebeddb4287b@mail.gmail.com>
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Tsu-Fan Cheng <tfcheng@gmail.com> wrote: > Hi, > I have a pretty basic question: when I "df -H" my disk, the numbers > cant add up, > > > Filesystem Size Used Avail Capacity Mounted on > /dev/ad0c 484G 429G 17G 96% /ad0c > > > there should be more disk space available based on what is shown. why > is this like that?? This is default behavior. From tunefs(8): -m minfree Specify the percentage of space held back from normal users; the minimum free space threshold. The default value used is 8%. Note that lowering the threshold can adversely affect perfor- mance: +o Settings of 5% and less force space optimization to always be used which will greatly increase the overhead for file writes. +o The file system's ability to avoid fragmentation will be reduced when the total free space, including the reserve, drops below 15%. As free space approaches zero, throughput can degrade by up to a factor of three over the performance obtained at a 10% threshold. Your df output suggests your minfree is set to the default 8%; to confirm this: % dumpfs /dev/ad0c | grep minfree | cut -f 1-2 -- Sahil Tandon <sahil@tandon.net>
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