> From: Jack Bailey <jack@xxxxxxxxxxxxxxx>
> Date: Jan 8, 2008 3:17 AM
> To: centos@xxxxxxxxxx
>
> Hello All,
>
> Consider a CentOS-5.1 Xen server (2.6.18-53.1.4.el5xen) hosting two
> domains running CentOS-5.1 (2.6.18-53.1.4.el5). One domain has a fairly
> accurate clock, the other domain has a clock that gains ungodly amounts
> of time, roughly one minute every two or three minutes. For a fix, one
> suggestion is to run this command in DomU:
>
> echo 1 > /proc/sys/xen/independent_wallclock
>
> This didn't change anything. As an experiment, I wrote a script to call
> ntpd -q, sleep 60, and repeat indefinitely. Here are a couple of
> snippets of output:
>
> goodclock# ksh ./xenclockdrift
> ntpd: time slew +0.001211s
> ntpd: time slew +0.001200s
> ntpd: time slew +0.001855s
> ntpd: time slew +0.001532s
> ntpd: time slew +0.001603s
> ntpd: time slew +0.001320s
> ntpd: time slew +0.001931s
>
> badclock# ksh ./xenclockdrift
> ntpd: time slew -0.000193s
> ntpd: time set -57.356377s
> ntpd: time slew +0.002352s
> ntpd: time slew +0.003018s
> ntpd: time set -57.417488s
> ntpd: time slew +0.012089s
> ntpd: time slew -0.000985s
>
> These domains are fully virtualized and set up identically, except
> "badclock" is allocated two processors versus one processor for
> "goodclock". DomU's clock is running normally.
>
> Anyone know what's going or know how to fix it?
> Jack
I'm not sure with Xen, but on VMWare one should not be using NTP at
all. Time syncing should be done with the vmware tools and the host,
with NTP only running on the host (not the guests). Using NTP on a
vmware system will result in similar behavior to what you are seeing
here.
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