RE: troubleshooting slow I/O performance.
Date: Mon, 7 May 2018 13:40:12 -0400
Message-ID: <022d01d3e62a$74243060$5c6c9120$_at_rsiz.com>
one little wrinkle to add is the redundancy level you have chosen. Stefan mentioned the underlying possible raid and lun configuration.
IF multi-device underlying LUNs are hidden from Oracle and you have a redundancy other than external, it is possible to create an “anti-pattern” in ASM’s choices of failure group partner such that the same real physical disks are hit doubly or triply.
This is neither a recommendation for or against external redundancy, just make sure that it is not the problem.
If you current are NOT external redundancy, the trivial way to see if this is a problem is to create a tablespace with external redundancy and run an i/o test on it.
If your six 30TB LUNs don’t use parts of each other’s “trays” or other components in the physical stack this is not your problem a priori. But I have observed systems where some fraction of each disk is striped with mirror pairs across many disks and that is presented as a LUN and another fraction of the same disks is likewise built into a LUN. …And then these are presented to Oracle’s ASM as two different things. Hilarity ensues.
mwf
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Stefan Knecht
Sent: Monday, May 07, 2018 1:12 PM
To: Chris Stephens
Cc: oracle-l
Subject: Re: troubleshooting slow I/O performance.
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
-- // zztat - The Next-Gen Oracle Performance Monitoring and Reaction Framework! Visit us at <http://zztat.net/> zztat.net | _at_zztat_oracle | fb.me/zztat | zztat.net/blog/ -- http://www.freelists.org/webpage/oracle-lReceived on Mon May 07 2018 - 19:40:12 CEST