RE: I/O performance

From: Allen, Brandon <Brandon.Allen_at_OneNeck.com>
Date: Fri, 8 Jun 2012 18:26:18 +0000
Message-ID: <A250F0C68C23514CA9F3DF63D60EE10E163C1883_at_onews31>



I think the 75% estimate is a good rule of thumb, but I don't think the explanation below is correct. I think if you run a test of only single-block random reads, you can indeed hit the calculated max IOPS of a disk drive. I think the reason for reducing the IOPS estimate to 75% for actual implementation planning is that in real-world usage many of the IOs will probably be larger sequential IOs (rather than random IOs), e.g. Full Table Scans, which will increase the observed transfer rate, but decrease the IOPS. Notice that I've prefaced all my statements with "I *think*" - that's because I haven't actually tested these claims myself and I'm not a hardware expert, so feel free to correct me if I'm wrong.

Regards,
Brandon

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Taylor, Chris David

Of the approximate calculated IOPS, you can only count on about 75% of that capacity as you will never reach the full calculated IOPS because there is a direct relationship between disk utilization and response time - as utilization increases, response time decreases, so only count on about 75% of the calculated IOPS per disk. (I tried to find a specific link illustrating this relationship but gave up)


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http://www.freelists.org/webpage/oracle-l Received on Fri Jun 08 2012 - 13:26:18 CDT

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