On Tue, Mar 08, 2011 at 03:26:34PM -0800, Chuck Swiger wrote: > >> You are better off running ntpdate (or sntp) periodically via cron in > >> the DomUs. > > > > Perhaps in certain cases, but not across the board. > > I'd be happy to review counterexamples to my generalization....
I'd say it depends on the VM. For instance, Fedora 14 running in kvm on Fedora 14. There are four clocksources available in the guest system: kvm-clock tsc hpet acpi_pm. With each of them the frequency seems to be stable, even when the host or guest CPU is heavily loaded. The kvm-clock and hpet clocks seem to be running at same rate as the host's system clock, tsc at the real CPU's rate and acpi_pm is off by few tens of ppm. Here is a rv output from ntpd running in the guest with the tsc clock, the host is not synchronized: associd=0 status=0615 leap_none, sync_ntp, 1 event, clock_sync, version="ntpd 4.2.6p2@1.2194-o Mon Aug 23 12:18:41 UTC 2010 (1)", processor="x86_64", system="Linux/2.6.35.2-9.fc14.x86_64", leap=00, stratum=3, precision=-23, rootdelay=128.742, rootdisp=41.165, refid=10.34.32.125, reftime=d121ddab.0ab5b995 Wed, Mar 9 2011 6:06:19.041, clock=d121ddab.5dd3a440 Wed, Mar 9 2011 6:06:19.366, peer=47730, tc=4, mintc=3, offset=-0.013, frequency=22.454, sys_jitter=0.011, clk_jitter=0.016, clk_wander=0.028 -- Miroslav Lichvar _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions
