[ntp:questions] orphan mode, manycast, and virtualization

Rob nomail at example.com
Mon Sep 9 17:55:33 UTC 2013

unruh <unruh at invalid.ca> wrote:
> On 2013-09-09, Horvath Bob-BHORVAT1 <Bob.Horvath at motorolasolutions.com> wrote:
>> Another question if you guys have the time :),
>> We situations in which we have almost everything deployed as virtualized servers running inside of VMware ESXi.    It seems like the recommendation on time synchronization  with ESXi has changed from release to release.  It seems to boil down to one of the following:
>> A)     Run ntpd on the bare iron at the ESXi layer and let it change the virtual hardware clock (without ntpd running on VMs)
>> B)      Run ntpd on the bare iron at the ESXi layer and let ntpd on the VMs use it as a time source
>> C)      Run ntpd on all the VMs and point them to as many "good" ntp servers that you can find whether in its own ESXi or another physical server's ntpd.
> Use A. C is horrible, and it is very easy for the VM's to exceed the
> 500PPM ntpd threshold. And ntpd does a really horrible job of
> disciplining a clock that keeps changing and losing time on a short
> timescale. It is designed for a clock with a bad, but consistant, rate.
> By design it takes a long time to settle down. And having something like
> your VM clock going to sleep for random amounts of time will drive ntpd
> crazy. That rules out 2 or 3. 
> Any virtual machine should get its time from the underlying system. 

Meaningless babble from someone without experience with ESXi.
Bob, please don't base your decisions on this.

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