Date: Tue, 28 Jun 2005 11:21:26 +0200 From: Roman Neuhauser <neuhauser@sigpipe.cz> To: freebsd-stable@FreeBSD.ORG, Michael Schuh <michael.schuh@gmail.com> Subject: Re: FreeBSD MySQL still WAY slower than Linux Message-ID: <20050628092126.GB48140@isis.sigpipe.cz> In-Reply-To: <200506211451.j5LEpA2W024350@lurza.secnetix.de> References: <1dbad315050621051525f4c6fc@mail.gmail.com> <200506211451.j5LEpA2W024350@lurza.secnetix.de>
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# olli@lurza.secnetix.de / 2005-06-21 16:51:10 +0200:
> For accurate measurements and comparisons, you have to make
> sure to use _exactly_ the same physical location on the
> disk.
No you don't. You want to make a side-by-side comparison
of two products, and if one of them underperforms, it just
underperforms. You cannot use a poor location selection
strategy in the driver as an excuse for poor operation.
In all honesty, I'm getting somewhat irritated by all the
"dd is meaningless performance measurement tool, use something
real" and similar arguments: dd is a real command for real
work, and if it shows abysmal performance of sequential writes,
then there's a problem.
> But then again -- as others have already mentioned, serial
> write speed is not the most important factor for database
> performance (although the WAL journal files of advanced
> transactional databases like PostgreSQL are written in a
> sequential way), so the usefulness of this "benchmark" is
> very debatable.
Well, how about a few GB large table physically ordered
("clustered") on a column, that goes through repeated sequential
scans? This *is* a real-world situation, and every bit of speed
counts (the live server I'm talking about has the database on SCSI
disks, but development machines frequently differ).
--
How many Vietnam vets does it take to screw in a light bulb?
You don't know, man. You don't KNOW.
Cause you weren't THERE. http://bash.org/?255991
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