Date: Tue, 28 Jun 2005 19:13:24 +0200 From: Claus Guttesen <kometen@gmail.com> To: Roman Neuhauser <neuhauser@sigpipe.cz> Cc: Michael Schuh <michael.schuh@gmail.com>, freebsd-stable@freebsd.org Subject: Re: FreeBSD MySQL still WAY slower than Linux Message-ID: <b41c75520506281013da20de5@mail.gmail.com> In-Reply-To: <20050628163928.GA51923@isis.sigpipe.cz> References: <1dbad315050621051525f4c6fc@mail.gmail.com> <200506211451.j5LEpA2W024350@lurza.secnetix.de> <20050628092126.GB48140@isis.sigpipe.cz> <1119973124.7900.20.camel@zappa.Chelsea-Ct.Org> <20050628163928.GA51923@isis.sigpipe.cz>
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> > (Note that however good or bad it may be, the "location selection > > strategy in the driver" can only lay out data within the confines of > > the partition.) Now, I do a "dd" test and find that the "outside" OS > > is almost twice as fast as the other. Would it be wise to conclude > > that the slower OS is woefully inefficient compared to the faster one? > > Suppose both tests turn out to take roughly the same time. Should I > > conclude that the OS residing on the "inside" is just as efficient as > > the other OS? > ... rendering this completely irrelevant. > I have seen people come to a freebsd list with completely flawed > comparisons or benchmarks: OSs installed on different partitions > side by side, not taking VM cache into account, whatever, and be > told that their numbers are flawed. >=20 > I have also seen people test a specific subsystem (dd), and be told > that their numbers don't reflect real world. >=20 > And I have seen people test real world performance (install FreeBSD, > install MySQL, run a stress test, reformat, install Linux, install > MySQL, run a stress test) and get responses that try to make up > reasons why the bad results are the testers fault). Heck, if > installing an operating system, a database, and running it isn't > a real world test, I don't know what is. Even if the bug is "FreeBSD > puts /var/db/mysql in the wrong part of the disk" (then it's still > a problem in FreeBSD, not in the messenger). When one does the dd-test (on identical hardware), one should think that half the time FreeBSD would have the highest throughput, and the rest of the time Linux will, if the location of the partition that the test is performed on, is indeed located at a random location which should be the case when the test is performed often enough. When several people does this test and draws the conclusion that Linux (and FreeBSD 4.11) does this faster than 5.4/6, either only those who see this pattern post their numbers to this list, or Linux (and 4.11 to some degree) is indeed faster at this particular operation. And the test itself doesn't tell the complete story, but it does give an indication of what lies ahead. Arguing that the placement of the partion where the test is performed on is relevant, but then sometimes FreeBSD 5/6 should be faster. regards Claus
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