Date: Mon, 5 Oct 1998 14:55:38 -0600 (MDT) From: "Kenneth D. Merry" <ken@plutotech.com> To: tlambert@primenet.com (Terry Lambert) Cc: oppermann@pipeline.ch, gpalmer@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG Subject: Re: filesystem safety and SCSI disk write caching Message-ID: <199810052055.OAA27658@panzer.plutotech.com> In-Reply-To: <199810051850.LAA23549@usr01.primenet.com> from Terry Lambert at "Oct 5, 98 06:50:04 pm"
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Terry Lambert wrote... > > > > > I can post (once again) the results of a Novell study on server usage > > > > > patterns. The 30,000 foot view for a typical server breaks down to: > > > > > > > > > > 75% reads > > > > > 15% writes > > > > > 8% directory search operations > > > > > 2% other > > > > > > I think that is very dependant on the server type. PC NetWare fileservers > > > probably have very different access patterns to (say) a web server or a mail > > > server. Let alone a news server. > > > > Is there a way to gather such statistics on FreeBSD? > > > > I'd like to run it on all my boxes (and others) to get representative > > figures. After that we can discuss optimizations. > > This would be a very good idea. > > It would be best to instrument at the lowest level, *below* where > soft updates does its implicit write gathering, and/or any elevator > sorting occurs. > > > I have suggested one set of instrumentation, which is interval sampling > of number of tagged commands outstanding, which would resolve once > and for all the current debate. Unfortunately, I don't have the > good firmware that Justin seems to have, and thus I can't really > make the measurements myself. It also seemed to me that the authors > of the CAM code would be in a better position about where to validly > determine max tag loading than I, and so would be better suited to > the task of coding up the statistics gathering. You can easily gather the statistics from the devstat code. The busy count will tell you how many transactions are oustanding for a particular device. The devstat code also keeps track of how many reads, writes, and other commands are sent to a drive. There's a program to dump out the statistics here: ftp://ftp.kdm.org/pub/FreeBSD/cam/ds.c I just updated it to grok the long generation size. (it was an int before) It doesn't matter for i386, but it does for the alpha. Ken -- Kenneth Merry ken@plutotech.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-fs" in the body of the message
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