[GRLUG] FYI - old mysql and new gear

[Ben Rousch]

On Mon, Sep 19, 2011 at 4:45 PM, Michael Mol <mikemol at gmail.com> wrote:
> 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.

How about putting it in a virtual machine that only has access to 8 cores?

-- 
 Ben Rousch
   brousch at gmail.com
   http://clusterbleep.net/

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