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Two Identical VMs, When testing processing speed one is significantly slower than other? Advice

  • May 24, 2013 at 5:11 am

    #277812

    Hello All

    I have created two VMs, with exact cloned setup.

    I am running a simple connection test where from a .NET application

    I connect to the instance

    declare a variable

    disconnect

    and report how long this took.

    With VM1 this test takes 2ms

    With VM2 this test takes 8ms

    Everything, and I mean everything about these VMs is identical.

    Can someone explain what troubleshooting can be done to determine the reason for the difference.

    Same results are replicated locally (so not a network issue as it would use shared memory)

    What goes on within sql server from listening for the connection, processing the variable declaration that can cause such a significant difference.

    Thanks for your help in advance

  • May 24, 2013 at 6:26 am

    #1618224

    Hi

    You can catch the execution plans for the query on both servers and comparing them you'd probably come up to the reason why their duration differ.

    You'd better clean the cache (dbcc freeproccache, dbcc dropcleanbuffers, dbcc freesessioncache) before performing the test.

    Regards,

    IgorMi

    Igor Micev,
    My blog: www.igormicev.com

  • May 24, 2013 at 6:55 am

    #1618247

    I cleared the cache and same results as before

    I don't think an execution plan is generated as I only declare a variable

  • May 24, 2013 at 7:15 am

    #1618261

    Ok. I thought you use another query.

    Then, are the settings (ANSI_NULLS, QUOTED_IDENTIFIER, ...) for your connection (OLE DB, ODBC) identical with the settings on both servers?

    Regards

    IgorMi

    Igor Micev,
    My blog: www.igormicev.com

  • May 24, 2013 at 9:09 am

    #1618338

    Yes exactly the same unfortunately.

    Anything you can think of would be OK i just need some ideas of what to check

  • May 24, 2013 at 10:26 am

    #1618377

    One thing i have noticed is when using Performance Monitor to monitor

    \SQLServer:Transactions\Transactions

    On the Box VM1 that performs with only 1ms latency this counter is static and doesn't change

    On the Box VM2 that performs with higher latency 8ms this counter has huge spikes when i run my test.

    What could explain that?

  • May 24, 2013 at 11:48 am

    #1618398

    Can also see a CPU spike that isn't present on the identical other VM

  • May 24, 2013 at 2:52 pm

    #1618443

    How are you connecting? Windows auth or sql auth?

    Are both VMs talking to the same domain controller?

  • May 24, 2013 at 2:55 pm

    #1618444

    Is it possible that the instance on VM2 has some kind of log on monitoring (triggers) or tracing (to a table) enabled?

  • May 24, 2013 at 6:14 pm

    #1618489

    windows auth and sql auth produce the same results

    Yes i will try and look for a trigger etc that

    thanks for the suggestions i will post a solution if i find one

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