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Hyperthreading Question

  • October 5, 2006 at 10:26 am

    #172923

    I posted a question in the SS 2000 General section about hyperthreading and SQL Server 2000...  but the same question really applies to 2005... so I will repeat it here...

    According to MS, Windows Server 2003 is hyperthread technology (HTT) aware (2000 is not) and SQL Server 2000 at SP3 and beyond should run just fine with HTT turned on.  There are still lots of Google hits that say you should not use HTT and SQL Server; but they aren't necessarily dated articles, and do not mention service pack levels.  The advice in the past has always been to disable it.

    We currently have at least 16 machines running SQL Server 2000 and since HTT is turned on by default, it is on.  If this is not the proper direction then I need to make a case for the adjustment - and I can't do that yet.

    So, how about it?  What is the current status?  And if "off" is the recommendation, why?

    The usual discussion against using it is that SQL Server is thread intensive and threads get assigned to the wrong processor, etc., and sometimes cannot distinguish themselves from each other.  If MS and Intel both say HTT and SQL are okay... is it?

    Thanks for your responses.

    Thank-you,
    David Russell
    Any Cloud, Any Database, Oracle since 1982

  • October 5, 2006 at 1:12 pm

    #664439

    There is not a simple answer to this as it depends on both the load being applied to the server and the type of load. I have found personally that on most of our heavily loaded boxes that turning off HT increases performance but this will not apply to everyone.

    Anyway there is a good article here on it by one of the sql server team

    http://blogs.msdn.com/slavao/archive/2005/11/12/492119.aspx

    But the basic answer is try it with and try it without

    hth

     

    David

  • October 5, 2006 at 3:20 pm

    #664466

    Thank you David Scotland for an excellent link.  Sure seems like there is no conclusive answer without testing under load - which is often difficult to get the load in an environment where changes don't have to go through committee and/or CM.

    I would still like to hear more on the subject if people care to respond.

    and thanks again for the link.

    Thank-you,
    David Russell
    Any Cloud, Any Database, Oracle since 1982

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