Re: Linux, i/o scheduler and ASM

From: Kevin Closson <>
Date: Fri, 22 Apr 2011 14:21:07 -0700 (PDT)
Message-ID: <>

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)" <> To: "" <> 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.

Received on Fri Apr 22 2011 - 16:21:07 CDT

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