[ntp:questions] Timekeeping on Windows 2008r2 VM on Linux QEMU/KVM

Sander Smeenk ssmeenk at freshdot.net
Wed Jan 21 14:48:44 UTC 2015

Quoting Terje Mathisen (terje.mathisen at tmsw.no):

> a) You should not run ntpdate, instead you use the -q option to ntpd to
> handle any initial time steps.

What is actually wrong with running ntpdate to initially sync a clock?
Why is the ntpdate.exe binary provided when 'we' shouldnt use it?
Keep in mind that i 'just want to get to seconds accuracy' before i
start ntpd. 

> b) All the delay/offset/jitter times are measured in ms, not seconds!

I actually knew that. I made that mistake on this list before.
However it is also not relevant to the issues i am experiencing. Wether
it's microseconds or seconds, the jumps in offset/jitter are abnormal

> c) It seems that you have an ntp.drift file which contains "500"!

Indeed i did. That file was probably written by ntpd after the first run
going completely haywire. I removed it from the configuration. No change
to the issues i'm experiencing.

> d) I suspect that the QEMU/KVM virtualization of the Windows
> environment is faulty, i.e. the baseline frequency of your emulated
> hardware is badly wrong!

Wouldn't you expect to see the same issues on other VMs running on that
particular hypervisor host then?

> Can you run ntpd on the host machine and simply setup the client OS to
> be timesynced to the host?

I guess not. Linux VMs dont essentially need to run ntp to keep their
time synced if they use the correct clock source (kvm_clock) and the
host is properly configured, but i would have no clue if Windows is able
to do such stuff, let alone how. :(

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