[ntp:questions] Win7: ntpd adjusting time backwards

unruh unruh at invalid.ca
Thu Dec 13 23:06:59 UTC 2012

On 2012-12-13, Jeroen Mostert <jmostert at xs4all.nl> wrote:
> On 2012-12-13 09:08, David Woolley wrote:
>> Jeroen Mostert wrote:
>>> negatively affect performance of the host (which makes sense, since driving
>>> all virtuals with 1000 interrupts/sec can't be easy). Even so,
>> You wouldn't expect 1ms ticks. You might get 20 ticks back to back, and then a
>> gap of 20ms, or even larger numbers. VMs generally only get a virtual 1 second
>> per second as a long term average.
> If your virtualization is that poor, get a refund. :-) However, it's certainly 
> true that you cannot count on high-frequency ticks in a VM. There's simply not 
> enough horsepower on the guest to achieve that, unless you've got a one-to-one 
> mapping between actual and virtual hardware (and then there's not much point to 
> virtualizing).
>> There has been conflicting advice on running ntpd on VMs, but I suspect the
>> current advice to run it is an easy way of getting coarse timing right. Fine
>> timing should use the host timing and any special VM support for the OS.
> I agree. In the case of Windows on VMWare, however, there doesn't seem to be any.

Perhaps you should follow the advice you gave in the first sentence of
you response. 


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