[ntp:questions] Win7: ntpd adjusting time backwards

Jeroen Mostert jmostert at xs4all.nl
Thu Dec 13 23:25:45 UTC 2012


On 2012-12-14 00:06, unruh wrote:
> 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.
>
I'm an engineer. I don't pay bills, I just foot new ones working around the 
limitations caused by the people paying the bills.

-- 
J.



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