direct IO performance - Veritas Volume Manager

This is a discussion on direct IO performance - Veritas Volume Manager ; I've read in several places that the best mount option for an Oracle database is convsync=direct. I've tried this and my performance decreased. Some process increased in time by 50%. Any suggestions?...

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Thread: direct IO performance

  1. direct IO performance


    I've read in several places that the best mount option for an Oracle database
    is convsync=direct. I've tried this and my performance decreased. Some
    process increased in time by 50%. Any suggestions?

  2. Re: direct IO performance

    Quick IO which is part of database edition for oracle

    Michael wrote:
    > I've read in several places that the best mount option for an Oracle database
    > is convsync=direct. I've tried this and my performance decreased. Some
    > process increased in time by 50%. Any suggestions?


  3. Re: direct IO performance


    We don't have Quick IO and it is too expensive. Veritas says there should
    be an improvement with direct IO, which I can't see. So I'm hesitant to
    believe the claim that quick io is better.

    Me wrote:
    >Quick IO which is part of database edition for oracle
    >
    >Michael wrote:
    >> I've read in several places that the best mount option for an Oracle database
    >> is convsync=direct. I've tried this and my performance decreased.

    Some
    >> process increased in time by 50%. Any suggestions?



  4. Re: direct IO performance

    There is always a trade-off between speed and reliability.


    So, if you want speed, here is what you can set for mount options:

    logging mode:
    tmplog = very fast, but if the system crashes, you might have
    some loss (almost always a fsck)


    cache mode:
    mincache=tmpcache

    Again, you data will be lost when the system goes down


    Now, for Oracle, you have to specify the convosync=direct option



    If you need to test Quick IO, please speak to support (or your sales
    rep.). They will give you downlaod instructions (and temp. key) so that
    you can test IO performance on Quick IO





    michael wrote:
    > We don't have Quick IO and it is too expensive. Veritas says there should
    > be an improvement with direct IO, which I can't see. So I'm hesitant to
    > believe the claim that quick io is better.
    >
    > Me wrote:
    >
    >>Quick IO which is part of database edition for oracle
    >>
    >>Michael wrote:
    >>
    >>>I've read in several places that the best mount option for an Oracle database
    >>>is convsync=direct. I've tried this and my performance decreased.

    >
    > Some
    >
    >>>process increased in time by 50%. Any suggestions?

    >
    >


  5. Re: direct IO performance


    I have set the convsync=direct. That is what made performance degrade.



  6. Re: direct IO performance

    and the other options ?

    have you changed the log or cache options ?


    the convsync option is because Oracle uses ASYNC IO. If you do not use
    that, you do not need to set the convsync option




    Michael wrote:
    > I have set the convsync=direct. That is what made performance degrade.
    >
    >


  7. Re: direct IO performance


    Not the log.

    The mincache is set to direct.

    Asynch io is on in Oracle.


  8. Re: direct IO performance


    Remember ONLY use this for DB devices, not for binaries, output files etc,
    filesystem performance for ouput files etc will be WORSE with this option,
    and SUBSTANTIALLY slower




    "Michael" wrote:
    >
    >I've read in several places that the best mount option for an Oracle database
    >is convsync=direct. I've tried this and my performance decreased. Some
    >process increased in time by 50%. Any suggestions?



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