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13 years, 5 months ago
I have a domain controller running in VM on Hyper-V, the time seems to be steadily getting faster, over the X-mas period it's 5 faster, which seems odd!
I know how to change the time and I belive we setup an NTP server on the DC and ensured time-sync was turned off on Hyper-V.
I don't really want to keep setting the time. Is there a reason why the time is fast?
Dec 29, 2009 at 10:06
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With VM's you
always want the host to sync the guests, it's the only reliable way.
I realise this can create an infinite loop if the hosts are member servers of the domain, but every workaround I've tried (VMware server in my case) doesn't actually solve the problem.
If you run a good monitoring system (eg, Nagios) consider checking clock skew against the global NTP pool, or a reliable *nix based system (that's not a VM itself) running the NTPD package.
Dec 29, 2009 at 13:15
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VMs never keep accurate time (meaning they always have bad virtual CPU stats too), the only way to make sure they're accurate
enough is to have them sync with a physical clock. This can be done either by syncing with the host and having all the hosts time correct via NTP or via having the VMs get their time via NTP with frequent checks - either method works but the former is probably the easiest.
Jan 4, 2010 at 11:15
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All the prior answers seem reasonable, but let me add this.
Indeed, timekeeping inside a VM is a problematic issue, which brings up multiple possible solutions.
Set up another DC on an iron box, and have that be the authoritative time source
Set your VM DC to sync time from an external source more frequently - say every 10 minutes. Registry reference in this KB:
816042 Even simpler, use something like an
Atomic Clock sync tool on the DC, and set its frequency to 10-15 minutes Another
question on Serverfault had a similar problem, and ruled out the hardware clock by running the same VM in VMware Server, and found that the problem lies with Hyper-V.
Jan 5, 2010 at 14:57
Mike Fiedler Mike Fiedler
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Is there a reason you can't sync to an external source, such as one of the Internet time services? If you're having such a problem with drift just sync hourly, or whatever other period you feel might be suitable.
Jan 4, 2010 at 11:28
John Gardeniers John Gardeniers
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Globally we have the same problem under VMWare, it's due to the CPU Time synchronisation.
In fact you need to set up your Guess parameters under Hyper-V to be sync with your Host CPU clock frequency.
Jan 4, 2010 at 13:12
Dr I Dr I
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