[ntp:questions] NTP Servers in virtual machines

William Unruh unruh at invalid.ca
Mon Jun 23 23:11:29 UTC 2014


On 2014-06-23, Rob Heemskerk <rob.heemskerk at gmail.com> wrote:
> Hi,
>
> Why are NTP Servers running on virtualized hardware (vmware) unsuitable to serve time to clients?
>

Because the virtual clock does not tick regularly. The real clock does.

> I've read this statement several times but can't find a good motivation. I've searched the official documentation, FAQ, the NTP support wiki, this news group, google search.
>
> I found this in the support wiki but it seems outdated: 
> NTP server was not designed to run inside of a virtual machine. It requires a high resolution system clock, with response times to clock interrupts that are serviced with a high level of accuracy.  
>
> As kernels are tickles nowadays response times to clock interrupts and (interrupt backlogs) do not seem to be relevant anymore.  
>
> Could we say it is safe to run ntp servers on a virtualized platform or do we still need a few (4?) dedicated pieces of hardware to run our internal NTP servers?  

You canrun ntp on the machine that runs the virtual hardware, and tell
the virutal machines to get their time from the real system.

>
>



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