Date: Tue, 28 Jun 2005 13:03:04 -0400 From: Paul Mather <paul@gromit.dlib.vt.edu> To: Roman Neuhauser <neuhauser@sigpipe.cz> Cc: freebsd-stable@freebsd.org, Michael Schuh <michael.schuh@gmail.com> Subject: Re: FreeBSD MySQL still WAY slower than Linux Message-ID: <1119978184.7900.36.camel@zappa.Chelsea-Ct.Org> 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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On Tue, 2005-06-28 at 18:39 +0200, Roman Neuhauser wrote:
> # paul@gromit.dlib.vt.edu / 2005-06-28 11:38:44 -0400:
> > Note how the transfer rate for the "outside" is almost twice that of the
> > "inside." Suppose I run tests on two different operating systems, one
> > of which resides in a partition on the "inside" portion and the other in
> > one on the "outside" portion.
>
> Which is not the case according to the OP...
>
> > (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.
...especially when you've cut out the context of my reply. :-)
My apologies if it wasn't clear, but I was responding to your apparent
assertion that location does not matter in disk performance benchmarks.
If I had been responding to a specific aspect of the OP's benchmark (or
indeed anything the OP has said), I'm sure I would have quoted that to
make the context clear.
> 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.
>
> I have also seen people test a specific subsystem (dd), and be told
> that their numbers don't reflect real world.
>
> 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).
>
> I just wish people here were less defensive, that's all.
What you see as being defensive I see as being rigorous. If someone is
making a claim based upon a performance benchmark, people will quiz the
person conducting the benchmark to ascertain exactly how it has been
undertaken. To put any stock in a benchmark result, it is important to
be able to convince yourself it is a meaningful result. Well, at least
most people I've encountered believe that to be the case.
As it says in the BUGS section of the diskinfo man page: "There are in
order of increasing severity: lies, damn lies, statistics, and computer
benchmarks." ;-)
Cheers,
Paul.
--
e-mail: paul@gromit.dlib.vt.edu
"Without music to decorate it, time is just a bunch of boring production
deadlines or dates by which bills must be paid."
--- Frank Vincent Zappa
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