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Re: Testing Direct I/O

From: Mladen Gogala <>
Date: Mon, 13 Feb 2006 19:14:18 -0500
Message-Id: <>

On 02/13/2006 06:11:47 PM, Khemmanivanh, Somckit wrote:

> I saved and executed a few benchmark SQL statements pre-direct i/o, is
> this enough? Can I simply re-exexcute these benchmark statements?

Yes you can. Make sure those statements are laced with several "TRUNCATE" and "DROP" statements as they are the best for checking the benefits of direct I/O.

> What metrics should I be focusing on to "quantify" direct i/o benefit in
> my environment?

Well, the answer that is always correct is: "that depends". My favorite metrics in the winter months is the number of calories per serving. Alternatively, you can try with the BCHR. Allegedly, that is a good overall number which tells you how well your system would be performing had it not been for those pesky solar flares.

> What I don't want to do is switch to direct i/o and have performance
> decrease (i.e. temp TS space was de-buffered) or not understand what/why
> performance decreased...

In order to measure the performance impact of switching to direct I/O, it would be a good thing to measure your performance, in the first place. Completely illogical thing to do would be to develop a metrics to test your performance, then run a test to create a baseline against which you are testing, then switch to direct I/O, rerun the test and compare the results against the baseline. Unfortunately, my ESP powers are usually weak before summer so I cannot read your mind and create a test that would reflect your business model. My telepathic abilities increase exponentially if I am plied with copious quantities of Long Island ice tea, but as that is not the case, I can not help you.


Mladen Gogala

Received on Mon Feb 13 2006 - 18:14:18 CST

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