none
Turn on Auto-Mount and Disable TCP Chimney Offload...Why? RRS feed

  • Question

  • Could someone please explain for us why these two requirements exist as stated in the Protecting Hyper-V Machines TechNet article? (http://technet.microsoft.com/en-us/library/ff634200.aspx)

    • "You must turn on auto-mount on the host computer to enable virtual machine protection"
    • "You must disable TCP Chimney Offload"

    Also...

    • Do you disable TCP Chimney Offload on the Hyper-V hosts, the VM's, or both?
    • Wouldn't disabling TCP Chimney Offload potentially decrease performance?

    -Taylorbox

    Wednesday, July 28, 2010 8:46 PM

Answers

  • Hi,

     

    Automount should already be enabled by default - however if you disabled it,  then after DPM takes a snapshop of a running hyper-v guest, the OS won't mount the snapshot so we can revert it and the backup will fail.    Disabling tcp chimney is more of a "best practice" requirement as we found during the BETA that having it enabled can cause problems so we're recommending it be disabled on both the DPM server and the Hyper-V host being protected.  Performance hit should be negligable.


    Regards, Mike J [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Wednesday, July 28, 2010 9:36 PM
    Moderator

All replies

  • Hi,

     

    Automount should already be enabled by default - however if you disabled it,  then after DPM takes a snapshop of a running hyper-v guest, the OS won't mount the snapshot so we can revert it and the backup will fail.    Disabling tcp chimney is more of a "best practice" requirement as we found during the BETA that having it enabled can cause problems so we're recommending it be disabled on both the DPM server and the Hyper-V host being protected.  Performance hit should be negligable.


    Regards, Mike J [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Wednesday, July 28, 2010 9:36 PM
    Moderator
  • Thanks. Will disabling tcp chimney on the Hyper-V host cause any problems on the host's VM's if chimney is left enabled on the VM's?

    -Taylorbox

    Wednesday, July 28, 2010 11:07 PM
  • I have had many customer disable chimeny on the host and not worry about the guests and not cause any problems.  hope this helps.
    Regards, Mike J [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights.
    Thursday, July 29, 2010 11:51 PM
    Moderator