Date: Fri, 24 Jan 2003 16:03:31 -0800 (PST) From: Kevin Stevens <Kevin_Stevens@pursued-with.net> To: freebsd-questions@freebsd.org Subject: Filesystem tuning parameters Message-ID: <20030124160148.R12356@babelfish.pursued-with.net>
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I have a confusion about apparent conflicts between the minfree setting and time/space optimization. Per the manpage: minfree - Specify the percentage of space held back from normal users; the minimum free space threshold. The default value used is 8%. This value can be set to zero, however up to a factor of three in throughput will be lost over the performance obtained 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. space/time - The filesystem can either try to minimize the time spent allocat- ing blocks, or it can attempt to minimize the space fragmentation on the disk. Optimization for space has much higher overhead for file writes. The kernel normally changes the preference automat- ically as the percent fragmentation changes on the filesystem. I have a large (120GB) drive dedicated to data storage. I don't want to commit 10% (12GB) of space to free space, and I don't need nearly that much to avoid overflowing the volume. However, I want to maintain time optimization. When it says that "settings of 5% and less force space optimization to be used", is that still the case when you specify time optimization?? Also, why is "up to a factor of three in throughput" lost over the 10% setting? Is that another allusion to space optimization going into effect, or is there something else happening? I guess I don't understand the ramifications of the minfree setting. Any suggestions or references? Thanks! KeS To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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