Re: troubleshooting slow I/O performance.

From: Mladen Gogala <>
Date: Mon, 7 May 2018 12:55:34 -0400
Message-ID: <>

With all due respect, expensive clusters like that are usually engineered for performance when the hardware is chosen. You should have chosen 32Gbit FC adapters and either an all flash array like Xtrem_IO or Pure or a disk array with lots of cache. You should have calibrated your IO system for the needed number of IOPS. There are lots of cheap tools to do that, bonnie++ and iozone3 among the most popular ones. SLOB is a great tool, but for SLOB you need to have a database already installed. Once SLOB discovers that your IO is slow, there is very little you can do in terms of the underlying hardware.

On 05/07/2018 09:59 AM, Chris Stephens wrote:
> 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

Mladen Gogala
Database Consultant
Tel: (347) 321-1217

Received on Mon May 07 2018 - 18:55:34 CEST

Original text of this message