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Former Member

I/O scheduler in Linux guests

Hello SAP-VMware-Experts,

do you have any experience in comparing the Linux I/O schedulers when running in a VMware environment? We made some tests with a mixed (cpu, ram and disk utilizing) workload and saw that the "noop" is ~3% better.

http://kbase.redhat.com/faq/docs/DOC-5428

says similar things.

But I wonder if customers do really customize this value and if yes what experiences they have made.

Kind regards,

Matthias

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    Former Member
    Feb 12, 2010 at 10:27 AM

    Hi Matthias,

    that would be a nice topic for the next LinuxLab certification workshop to counter check!

    What do you think?

    Hannes

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    • Former Member Former Member

      According to tests which have been done during the SAP Linux Virtualization Certification Workshop in May 2010, we recommend to disable I/O scheduling in Virtual Machines (elevator = "noop"). See todays new version of SAP Note 1122388.

      Additionally, a customer provided test results they did with RHEL on vSphere. They performed tablespace create (write operation) and brconnect validate structure (read operation). See on the attached image how big the impact of the choosen scheduler was. In mixed I/O (reading and writing) the noop clearly provides more throughput.