Re: VMWare and Oracle IO

From: Stefan Koehler <contact_at_soocs.de>
Date: Tue, 7 Oct 2014 18:33:16 +0200 (CEST)
Message-ID: <80490813.233962.1412699596819.open-xchange_at_app09.ox.hosteurope.de>

Hi Jared,
a common example of the difference between service time (= I/O time that the SA usually measures) and host wait time (= I/O time from Oracle performance perspective). Referring to http://bartsjerps.wordpress.com/2011/03/04/io-bottleneck-linux/

What kind of I/O took 3.5 seconds - single block or multi Block I/O (in case of mb - what request size)? Any reason for using VMDKs?

I would also cross-check the queue size of the ESX host HBAs and the used multipathing options. However i mostly recommend to use VMware RDM (for performance, management and troubleshooting reasons) for the Oracle VMware infrastructure. There are some specific reasons to use the storage virtualization layer (e.g. VM snapshots), but go for RDM if they do not get used or the (enterprise) storage provides the capability.

You can do much more troubleshooting with direct SCSI (RDM throughput) in a VMware environment with Oracle databases.

Best Regards
Stefan Koehler

Oracle performance consultant and researcher http://www.soocs.de

> Jared Still <jkstill_at_gmail.com> hat am 7. Oktober 2014 um 17:29 geschrieben:
>
> Fellow Oracleites:
>
> I have been investigating a client database or two that have been experiencing IO problems since being virtualized via VMWare.
>
> SA's claim no IO issues, but we have seen an Oracle IO take up to 3.5 seconds.
> Seems slow to me.
>
> One thing I have learned is the the priority settings on VMWare disk shares can cause this issue for lower priority systems when the favored
> system(s) are requesting a lot of IO.
>
> What other gotcha's should we be looking for?
>
> Thanks!
>
> Jared Still
> Certifiable Oracle DBA and Part Time Perl Evangelist
> Principal at Pythian
> Pythian Blog http://www.pythian.com/blog/author/still/
> Oracle Blog: http://jkstill.blogspot.com
> Home Page: http://jaredstill.com

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Received on Tue Oct 07 2014 - 18:33:16 CEST