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From:Peter Zaitsev Date:May 7 2005 6:09am
Subject:Re: MySQL not using optimum disk throughput.
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On Fri, 2005-05-06 at 19:01, Greg Whalin wrote:
> What drives are you using?  For SCSI RAID, you definitly want deadline 
> scheduler.  That said, even after the switch to deadline, we saw our 
> Opteron's running way slow (compared to older slower Xeons).  Whatever 
> the problem is, we fought it for quite a while (though difficult to test 
> too much w/ production dbs) and ended up rolling back to 2.4.

One more thing to try, if you have smart RAID would be  "noop"
scheduler, to let  hardware to do the job.  Smart optimizations OS do to
reduce head movement may not make sense for RAID.     In practice I've
however seen close results. 

Also which storage engine are you using ?

One of the things which was changed in 2.6 for some hardware
configurations is  fsync() performance.      It was cases in some cases,
so it was instant. 

This for example explained in many cases why people moving from  IDE
devices to much faster SCSI devices may observe performance degradation
(IDE with 2.4 has typically fake fsync)


In general  we have very positive feedback from using Opterons with
MySQL at this point.  Sometimes it takes time to make it work right,
especially it was the case when they were new but when it flies. 
Practically same applies to EM64T - It is very good to have now two
inexpensive 64bit platforms available. 

We're getting some feedback about problems on some Fedora Core versions,
well this is "bleeding edge" distribution so I'm nothing but surprised.

SuSE both in SLES and Professional variants seems to work very well with
Opterons as well as recent RH EL.

Speaking about MySQL problems - if you have any MySQL issues on
Opterons,  please report them as bugs and we'll troubleshoot it.

> 
> Kevin Burton wrote:
> > Kevin Burton wrote:
> > 
> >> Greg Whalin wrote:
> >>
> >>>
> >>> Deadline was much faster.  Using sysbench:
> >>>
> >>> test:
> >>> sysbench --num-threads=16 --test=fileio --file-total-size=20G 
> >>> --file-test-mode=rndrw run
> >>
> >>
> >>
> > So... FYI.  I rebooted with elevator=deadline as a kernel param.
> > 
> > db2:~# cat /sys/block/sda/queue/scheduler
> > noop anticipatory [deadline] cfq
> > 
> > (which I assume means I'm now running deadline.  Is there any other way 
> > to find out?)
> > 
> > And no performance diff.  Note that you're benchmarks only show a 20M 
> > addition overhead.  We're about 60x too slow for these drives so I'm not 
> > sure what could be going on here :-/
> > 
> > Kevin
> > 
-- 
Peter Zaitsev, Senior Performance Engineer
Come to hear my talk at MySQL UC 2005  http://www.mysqluc.com/
MySQL AB, www.mysql.com


Thread
MySQL not using optimum disk throughput.Kevin Burton6 May
  • Re: MySQL not using optimum disk throughput.Dan Nelson7 May
RE: MySQL not using optimum disk throughput.Dathan Pattishall7 May
  • Re: MySQL not using optimum disk throughput.Greg Whalin7 May
    • Re: MySQL not using optimum disk throughput.Kevin Burton7 May
      • Re: MySQL not using optimum disk throughput.Greg Whalin7 May
        • Re: MySQL not using optimum disk throughput.Kevin Burton7 May
          • Re: MySQL not using optimum disk throughput.Kevin Burton7 May
            • Re: MySQL not using optimum disk throughput.Greg Whalin7 May
              • Re: MySQL not using optimum disk throughput.Kevin Burton7 May
                • Re: MySQL not using optimum disk throughput.Atle Veka7 May
                  • Re: MySQL not using optimum disk throughput.Kevin Burton7 May
                    • Re: MySQL not using optimum disk throughput.Atle Veka7 May
                  • Re: MySQL not using optimum disk throughput.Dan Nelson8 May
              • Re: MySQL not using optimum disk throughput.Peter Zaitsev7 May
                • Re: MySQL not using optimum disk throughput.Greg Whalin7 May
                  • Re: MySQL not using optimum disk throughput.Peter Zaitsev1 Jun
                    • RE: MySQL not using optimum disk throughput.Richard Dale1 Jun
        • Re: MySQL not using optimum disk throughput.Kevin Burton9 May
          • Re: MySQL not using optimum disk throughput.Greg Whalin9 May
            • Re: MySQL not using optimum disk throughput.Kevin Burton9 May
              • Re: MySQL not using optimum disk throughput.Greg Whalin9 May
                • Re: MySQL not using optimum disk throughput.Kevin Burton9 May
Re: MySQL not using optimum disk throughput.John David Duncan7 May
  • Re: MySQL not using optimum disk throughput.Peter Zaitsev7 May