Virtual DCs and Time Sync


Microsoft has just changed their argument regarding disabling the time synch integration services when running VMs (including DCs) .

Time Sync via Integration services is important when time service is not running ,like when you boot the machine or restore it from snapshot or resume.

So what should be done is to allow Time sync via Integration Services when the time sync cannot function ( revert from snapshot or resume) ,and get control back to windows time sync when it can function

Microsoft said “The recommendation now is to partially disable time synchronization between the host system and guest operating system acting as a domain controller. This enables your guest domain controller to synchronize time for the domain hierarchy, but protects it from having a time skew if it is restored from a Saved state

To do this and partially disable Time Sync via Integration services, we must change this registry key to zero :


“This command stops Windows Time service (W32Time) from using Hyper-V time synchronization integration when the guest domain controller’s operating system is started. With this setting disabled, the Hyper-V time synchronization provider is only used if the guest domain controller is rebooted or restored from a Saved state.”

Finally we got an officially answer about this topic. Furthermore, to know the authoritative time source for a machine , you can run this command w32tm /query /source

6 comments on “Virtual DCs and Time Sync

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