Article ID: 126926, created on Sep 17, 2015, last review on Sep 18, 2015

  • Applies to:
  • Virtuozzo 6.0


Windows Server 2012 and 2012 R2 virtual machines experience time drift after live migration between the servers with different CPU clock rate (frequency). Time inside the virtual machines goes faster or slower after migration, depending on whether the destination CPU is faster or slower.


The issue is recognized as a product bug with internal ID PSBM-39328.


The bug will be fixed in future Virtuozzo updates. As a workaround, set kernel.hyperv=0 system flag for affected virtual machines.

Boot flag can be added using either of the following ways:

  • Using Virtual Automation web-interface

Select the VM -> Hardware Settings -> CPU -> System flags field.

  • Manually modifying the virtual machine's configuration file (config.pvs is placed in the Home directory of a VM):

    1. Locate configuration file:

      ~# prlctl list -i w2k12VM | grep Home
      Home: /var/parallels/w2k12VM.pvm/

      Note!: replace w2k12VM with your actual VM name

    2. Stop Virtual Machine in question (configuration file must be modified on a stopped VM, otherwise changes might be lost):

      # prlctl stop w2k12VM
    3. Change the following part of the configuration file:

      ~# grep SystemFlags /var/parallels/w2k12VM.pvm/config.pvs
    4. Start Virtual Machine back:

      # prlctl start w2k12VM

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