Re: troubleshooting slow I/O performance.

From: Stefan Koehler <>
Date: Tue, 8 May 2018 10:13:26 +0200 (CEST)
Message-ID: <>

Hello Chris,
at first you need to identify where the time is spent in the whole I/O stack (e.g. I/O scheduler, SCSI, etc.).

For example you can do that with blktrace on Linux:

Anything further is related to this drill-down outcome :-)

Best Regards
Stefan Koehler

Independent Oracle performance consultant and researcher Website:
Twitter: _at_OracleSK

> Chris Stephens <> hat am 7. Mai 2018 um 15:59 geschrieben:
> We have a new 5 node 12.2 RAC system that is not performing the way we want. 
> The glaring issue is that "db file sequential read"'s are taking ~10ms. before i lob this over to the storage administrators, are there any possible areas in the clusterware/database configuration that I should investigate first? i have root access to all of the nodes. is there any information i can collect that would expedite the process of figuring out why we have such slow I/O times?
> slow i/o was discovered by running slob. if you don't know about that tool, you should. we all owe kevin a debt of gratitude. ;)
> if nothing else, i hope to learn a little more about storage than i currently know (which isn't much).
> thanks for any help.  
> chris

Received on Tue May 08 2018 - 10:13:26 CEST

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