Date: Fri, 15 Oct 1999 16:14:29 -0600 (MDT) From: "Kenneth D. Merry" <ken@kdm.org> To: groudier@club-internet.fr (Gerard Roudier) Cc: cdf.lists@fxp.org (Chris D. Faulhaber), gallatin@cs.duke.edu (Andrew Gallatin), scsi@FreeBSD.ORG Subject: Re: FreeBSD 3.2 / Slow SCSI Dell PowerEdge 4300 Message-ID: <199910152214.QAA52284@panzer.kdm.org> In-Reply-To: <Pine.LNX.3.95.991015234921.543A-100000@localhost> from Gerard Roudier at "Oct 16, 1999 00:09:29 am"
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Gerard Roudier wrote... > On Fri, 15 Oct 1999, Kenneth D. Merry wrote: > > Gerard Roudier wrote... > > > For the DCAS, the decrease of performances has been observed for > > > sequential write IOs that is a great stress for a disk when write behing > > > caching is enabled with tags enabled, but still nothing has been reported > > > for read and especially multithreaded read IOs. Castrating a disk model > > > regarding tags due to such unreaslistic results has been unserious in my > > > opinion. > > > > In the case of the DCAS drives, the PR author (see kern/10398) did > > extensive tests with bonnie, and found that both the number of random seeks > > Random IO decrease is surprising given the small number of transactions > per second and the small IO bandwidth needed for the test. Anyway, such a > testing just makes the drive prefetch data and then makes it have to throw > prefetched data away. Using simultaneous sequential IO streams may take > advantage of the prefetching (such a testing is more realistic than Bonnie > seeks). Some simple combination of usual UNIX commands is sometimes a far > better testing than inappropriate benchmarks. Well, if you've got ideas for a better benchmark, why not write one, or point people to a better benchmark? Bonnie may not be a "great" benchmark, but it's better than a simple sequential I/O benchmark. And it's more precise than just telling people to run a bunch of random UNIX commands. Greg Lehey's rawio program (ftp://ftp.lemis.com/pub/rawio.tar.gz) seems like it might do a reasonable job (I haven't used it, however), but the only problem with it is that it works on raw devices. (There's not much you can do to get around that if you want to avoid possible buffer cache interactions that come with going through the filesystem.) Ken -- Kenneth Merry ken@kdm.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-scsi" in the body of the message
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