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Hyper-V File Copy Speeds Slow, from Host initiated copies

    Question

  • Here is a diagram of the problem.

     

    ------------

     

    [Hyper-v Host (2k8 R2) \\HOST ] [Guest (2k8 R2)]

     

    Run from Hyper-V Host OS:  copy \\Guest\Share\bigfile.zip \\Host\Share\

    Result: Transfering @ 500kb/sec

     

    Run from Guest OS on same Hyper-V Host:  copy \\Guest\Share\bigfile.zip \\Host\Share\

    Result: Transferring @ 100MB/sec

     

    What could be causing this?  No A/V on either host or guest OS.

    Thursday, June 23, 2011 1:44 PM

Answers

  • The answer to my troubles was disabling ALL instances of TCP Offloading, and Recieve Side Scaling on the HOST's LAN NIC.  We tested and it didn't appear to be necassary to do this on the VM NIC.  Hope this helps someone.
    • Marked as answer by mikeyuf Wednesday, June 29, 2011 6:45 PM
    Wednesday, June 29, 2011 6:45 PM

All replies

  • Hi,

     

    Please check the following post to see whether you can resolve the issue.

     

    Slow SMB copy from VM to Host Hyper-V R2

    http://social.technet.microsoft.com/Forums/en-US/winserverhyperv/thread/1cf03b62-2dde-4d06-8722-dc4548bc338c/

     

     

    Best Regards,

    Vincent Hu

     

    Thursday, June 23, 2011 2:09 PM
    Moderator
  • Hotfix from stated thread is already installed and did not resolve the issue.
    Thursday, June 23, 2011 2:37 PM
  • UPDATE:  Ok did more testing...

     

    The slow transfer seems to be ONLY from the Server 2008 R2 HyperV Host and 2008 R2 VM's.

    I tested with a Windows 7 VM, and tranfer works fine both ways.

     

    The Win 7 VM was on the same virtual switch, so that rules that out as well in my opinion.

    It must be a setting or virtual driver on the Server 2008 R2 VM's...?

     

    Here are my tests:

    Tests

    IBM Server1 to IBM Server2  
     Initiated from Server 1    FAST
     Inititiated from Server 2   FAST

    IBM Server2 to IBM Server1
     Initiated from Server 1    FAST
     Initiated from SErver 2    FAST

    IBM Server1 to Local Virtual Machine
     Initiated from Server1    FAST
     Initiated from Local VM on Server 1  FAST

    IBM VM( on Server1) to Server1
     Initiated from Server1    SUPER SLOW 500KB
     Initiated from VM    FAST


    IBM Server2 to Local Virtual Machine
     Initiated from Server2    FAST
     Initiated from Local VM on Server2  FAST

    IBM VM( on Server2) to Server2
     Initiated from Server2    SUPER SLOW 500KB
     Initiated from VM    FAST

    IBM Physical PC to Server1
     Initiated from PC    FAST
     Inititalted from Server1   FAST

    IBM Server1 to Physical PC
     Initiated from PC    FAST
     Inititalted from Server1   FAST

    IBM Physical PC to Server2
     Initiated from PC    FAST
     Inititalted from Server2   FAST

    IBM Server2 to Physical PC
     Initiated from PC    FAST
     Inititalted from Server2   FAST

    IBM Server1 to Win 7 VM on Server1
     Initated from VM    FAST
     Inititated from Server1    FAST

    IBM Win7 VM on Server1 to Server1
     Initiated from VM    FAST
     Initiated from Server1    FAST

     

    This is driving me nuts!

     

    Friday, June 24, 2011 4:00 PM
  • Alright, here is some more information, the slow culprits are ALL domain conrollers.

     

    I set up a test 2008 R2 VM machine, tested before and after joining it to the domain, and it transfers fast before and after.

     

    Anyone have any ideas why a domain controller would slow down file transfers?

    Friday, June 24, 2011 9:24 PM
  • Anyone?
    Sunday, June 26, 2011 11:43 PM
  • The answer to my troubles was disabling ALL instances of TCP Offloading, and Recieve Side Scaling on the HOST's LAN NIC.  We tested and it didn't appear to be necassary to do this on the VM NIC.  Hope this helps someone.
    • Marked as answer by mikeyuf Wednesday, June 29, 2011 6:45 PM
    Wednesday, June 29, 2011 6:45 PM