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calculate Avg.Disk Queue length

  • November 23, 2009 at 11:59 pm

    #143110

    Hi,

    Below are the Avg.Disk Queue length values from Perfmon. As the best practice, Avg.Disk Queue length shroud be <2. So how to calculate the below, because I did not see any units for Avg.Disk queue length

    0.022792896

    0.018652975

    0.020772934

    0.01875964

    0.021059596

    thanks

  • November 26, 2009 at 12:22 pm

    #1084692

    Could you please advice me on how to calculate Disk Queue length..

  • November 27, 2009 at 3:55 am

    #1084840

    I'm unclear on what you're asking. The output from Perfmon already IS the Average Disk Queue Length, there's no calculation involved...and the values you've got there look absolutely fine.

  • November 27, 2009 at 9:01 am

    #1084940

    Avg Disk Queue Length is essentially useless in modern times where the IO subsystem is almost always NOT single-spindle based.

    use avg disk sec/read and avg disk sec/write from perfmon. also check out the virtual file stats DMV for sql server's version of file IO stall information.

    Best,
    Kevin G. Boles
    SQL Server Consultant
    SQL MVP 2007-2012
    TheSQLGuru on googles mail service

  • November 27, 2009 at 9:32 am

    #1084958

    You can read this article to capture IO Stats

    http://www.mssqltips.com/tip.asp?tip=1416

    Regards

    SNM

    Try Free Microsoft SQL Server Data Collector & Performance Monitor.

    http://www.analyticsperformance.com[/url]

    @nalyticsperformance - Microsoft SQL Server & Windows Server Free Data Collector

  • November 27, 2009 at 12:19 pm

    #1085005

    Considering Your specific question,

    and assuming you are using the Perfmon with the default settings for the performance counter mentioned you have to make a product by 100 every measured values to get the real que length.

    The "100" represents the default "Scale" factor by witch the measures are weighted for better graphical representation.

    Check the properties of the performance counter for exact value of the Scale factor.

    Avg.Disk queue length has no standard unit measure because it represent the average count of read/write task per second witch had to be scheduled for later execution because of lack in resources.

    I hope this was Your question.

    By.

  • November 29, 2009 at 1:41 pm

    #1085161

    ok.. these are the values I got from perfmon for

    0.022792896

    0.018652975

    So do I need to divide these numbers with any value?

    If I get a value 2.0 or >2.0, then we have a disk IO problem right?

    From above values, we do NOT have any issue with Avg Disk Queue length right?

    thanks

  • November 29, 2009 at 5:05 pm

    #1085202

    Mani-584606 (11/29/2009)

    ok.. these are the values I got from perfmon for

    0.022792896

    0.018652975

    So do I need to divide these numbers with any value?

    If I get a value 2.0 or >2.0, then we have a disk IO problem right?

    From above values, we do NOT have any issue with Avg Disk Queue length right?

    thanks

    Did you read my reply above about NOT using ADQ for IO analysis??

    Best,
    Kevin G. Boles
    SQL Server Consultant
    SQL MVP 2007-2012
    TheSQLGuru on googles mail service

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