Re: Linux, i/o scheduler and ASM
From: Kevin Closson <ora_kclosson_at_yahoo.com>
Date: Fri, 22 Apr 2011 14:21:07 -0700 (PDT)
Message-ID: <834300.73164.qm_at_web161712.mail.bf1.yahoo.com>
The linux I/O scheduler has little to do with random small I/Os (e.g., db file sequential read, db file parallel write,etc). They have most to do with opportunities to coalesce adjacent I/O requests thus condensing the number of physical transfers with larger payloads. I wouldn't ever expect to see much. We had reasons to explore this in cellsrv (the Exadata Storage Server software executable). However, if your large I/Os are buffered in hugepages memory there is even less the I/O schedulers can do to help/harm your I/O.
From: "CRISLER, JON A (ATTCORP)" <JC1706_at_att.com> To: "oracle-l_at_freelists.org" <oracle-l_at_freelists.org> Sent: Mon, April 18, 2011 8:51:01 AM
Subject: Linux, i/o scheduler and ASM
Date: Fri, 22 Apr 2011 14:21:07 -0700 (PDT)
Message-ID: <834300.73164.qm_at_web161712.mail.bf1.yahoo.com>
The linux I/O scheduler has little to do with random small I/Os (e.g., db file sequential read, db file parallel write,etc). They have most to do with opportunities to coalesce adjacent I/O requests thus condensing the number of physical transfers with larger payloads. I wouldn't ever expect to see much. We had reasons to explore this in cellsrv (the Exadata Storage Server software executable). However, if your large I/Os are buffered in hugepages memory there is even less the I/O schedulers can do to help/harm your I/O.
From: "CRISLER, JON A (ATTCORP)" <JC1706_at_att.com> To: "oracle-l_at_freelists.org" <oracle-l_at_freelists.org> Sent: Mon, April 18, 2011 8:51:01 AM
Subject: Linux, i/o scheduler and ASM
Has anybody played around with changing the Linux I/O scheduler when using ASM (11gR2) ? I am wondering if any performance differences are to be found in using CFQ vs. Deadline vs other options, especially in a large RAC / SAN environment. Right now we are using CFQ, and in my previous experiments on filesystems I did not get any noticeable difference in changing to deadline.
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