[GRLUG] FYI - old mysql and new gear

[Michael Mol]

On Mon, Sep 19, 2011 at 4:36 PM,  <scott.tanner at comcast.net> wrote:
> Just thought I'd share an interesting discovery with the group.  This may be
> common knowledge to others, but it was a bit of a surprise to me.   We're in
> the process of upgrading the servers which run our primary MySQL DB's
> (version 5.1):
>
>   Old Server                    New Server
> ---------------------------------------------------------
>    Sun X4200                 Silicon Mechanics R516
>     4 x 2.4GHz                 12 x 3.2GHz (+ HT = 24 threads)
>     16GB Ram                  144GB Ram
>   12 disks - SCSI             24 disks - SAS & SSD
>
>
> After getting the new servers setup and our databases copied over, I ran
> sysbench to get some performance benchmarks of the new servers.  Surprise  -
> performance was nearly identical or slightly worse.  I disabled HT, still no
> real improvement.   After a bit of searching on the web, I found the older
> versions of MySQL had issues with multi-threading beyond 8 threads.  I setup
> an init script to hot-remove CPU's via sysfs, and voila - performance
> increased substantially.   There are patches from Yahoo, Google, and Percona
> to correct this issue on the older MySQL versions, and the newer versions
> are supposedly better at handling 32+ threads.

Very interesting.

A thought...Rather than removing your extra cores, perhaps there's
some way to set CPU affinity, so MySQL is only allowed to use eight of
them? That way, the other processes on your system can stay out of the
way of your database server, and spend cycles on other cores.

If you get affinities working, you might also consider running
multiple instances of mysqld, putting different databases on different
sets of cores.


-- 
:wq

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