Re: mysql scaling questions

On Sun, Dec 30, 2007 at 02:18:31PM +0100, Kris Kennaway wrote:
Gergely CZUCZY wrote:
On Sat, Dec 01, 2007 at 12:22:34PM -1000, Jeff Roberson wrote:
On Sat, 1 Dec 2007, Gergely CZUCZY wrote:

On Sat, Dec 01, 2007 at 04:06:55PM -0500, Mike Tancsa wrote:
At 03:56 PM 12/1/2007, Gergely CZUCZY wrote:
I don't quite understand the question. It's the very same box, with
a dualboot configuration.
Fire up the 3ware controller's RAID management software and make sure the same write caching strategy is set for FreeBSD and Linux.
The
driver my default to different values.

i.e. under "controller settings" make sure "write cache" and "queuing" are the same values for linux and freebsd.
Let's get back to this on monday. I'm at home now, and the
box is at me workplace, still running a test (i can't reboot it).
Also, can you verify with a read-only test to see where it's at? I have not tested writes with that many threads. I notice mysql
goes much faster with a fresh table too. So can you blow away and recreate the sysbench tables and then do read-only? If that is
much slower we'll know there is some configuration problem or similar.
It will all be available here:
http://phoemix.harmless.hu/mysql/

Hi,

Sorry for the late reply, I was on vacation. I have a couple of comments about this:

* You are using some very old mysql versions and trying to compare between diferent versions. New minor releases in the 5.0 series had
very different performance, and you really need to be using at least 5.0.45 (I didn't notice a performance change between 5.0.45 and
5.0.51 but there was a big improvement in every release up to .45. In addition, versions older than (I think) .37 have serious
performance bugs).

I appreciate that you might be constrained by local requirements, but it's really not meaningful to compare different mysql versions if
your goal is to study OS performance.
It'd be a PITA to install the both versions. Maybe now, that the ports freeze is over, i can
do something. But honestly, every mysql version was faster on linux, than eny on FreeBSD,
even the .22 one was faster. We start work on Jan02, I will see what can I do.


* What database engine are you using? I have only tested with innodb but maybe you are using myisam? Please provide your exact
sysbench command lines.
MyISAM, of course. InnoDB is not any good with replication, and we need backup.

* Compare to my config file here:

http://people.freebsd.org/~kris/scaling/my.cnf

The default mysql config has very poor performance for innodb (you need at least innodb_thread_concurrency = 0 to disable some mysql
brain-death). Maybe tuning is required for myisam also.

* Also make sure you are using identical config settings on the two systems.
http://phoemix.harmless.hu/mysql/ verify yourself. Only the paths are
updated, but the main parameters are just the same.

* With the above, please compare read-only mode also (I think Jeff already asked you about this but I didnt see a reply). That will
allow us to calibrate what is going on.
http://phoemix.harmless.hu/mysql/ro-all.png
The graph is mistitled as Read-write, but it's a readonly test.


Sincerely,

Gergely Czuczy
mailto: gergely.czuczy@xxxxxxxxxxx

--
Weenies test. Geniuses solve problems that arise.

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