Date: Sun, 9 Mar 1997 01:16:11 -0500 (EST) From: "matthew c. mead" <mmead@goof.com> To: marcs@znep.com (Marc Slemko) Cc: isp@freebsd.org, hackers@freebsd.org Subject: Re: freebsd as a news server? Message-ID: <199703090616.BAA12521@goof.com> In-Reply-To: <Pine.BSF.3.95.970308230319.6158P-100000@alive.znep.com> from "Marc Slemko" at Mar 8, 97 11:14:06 pm
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Marc Slemko writes: > On Sat, 8 Mar 1997, matthew c. mead wrote: > > > Michael Smith writes: > > > matthew c. mead stands accused of saying: > > > > > > > > > > I really do suggest using -o noatime,async > > > > > on mounted news partitions too (for 2.2) > > > > > > > > This system is a 2.1.6 installation. Do these > > > > recommendations change based on that? Thanks for the replies! > > > > > No async support in 2.1.6, but I believe that noatime is supported. > > > > Hmm. No wonder I don't see any improvement in 2.1.6 > > mounting async and building the kernel. > > Try creating 5000 files, mounting async, then removing them. Try the same > thing mounted sync. If you are close to the box and the drives aren't too > quiet, you will be able to hear the difference in addition to just seeing > a speed improvement. You should only notice a trivial difference mounting > async for making the kernel; what mounting async does is change the fs so > metadata updates are done with bdwrite instead of bwrite. bwrite blocks > until the data is actually written to disk while bdwrite just marks the > buffer dirty and allows it to be delayed for a while before it is actually > written. When lots of files are being updated, allowing that buffering > speeds things up a good bit. Making a kernel is generally cpu limited so > mounting async doesn't help much; it wouldn't make any difference for raw > throughput to a single file either. > > The reason why mounting async can be dangerous is that it can leave the > metadata (ie. inode info) in an inconsistent state; I've never lost a fs > from it, just a few files that were being written around the time a system > crashed, but fsck often fails to automatically fix it. Hmm. The above seems to suggest that the practice of mounting async when doing a make work wouldn't help, but I recall it making a pretty measurable difference. What I meant in the question I asked was, considering that I'm running 2.1.6, mounting async probably doesn't make any difference. Is that the case? Or am I just not testing things that would make any difference? Thanks for the reply! -matt -- Matthew C. Mead mmead@goof.com http://www.goof.com/~mmead/
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