Hmm, I have been running dovecot inside xen for almost 3 years now
without any time issues. I checked my logs and I have no ntp time
reset messages for the last month.
I think it's more possible ntp is stepping the time instead of slewing
it (http://www.ntp.org/ntpfaq/NTP-s-algo.htm section 5.1.1.4), OR, the
ntp servers your using or network connection you have are giving you
lots of jitter. I personally try to pick 3 good low jitter, low
latency servers and 1 higher latency. Only running ntpd on the dom0
and nothing on the domU's.
Hmm, checking the lots on my home machine, even it doesn't have a time
reset log message, and it's network can be overloaded for hours at a
time.
Quoting Thierry DOSTES <tdostes@ibsm.cnrs-mrs.fr>:
Hi,
Here comes an extract from Debian Wiki about Xen to allow a domU to
keep its own time :
(...) your domU is likely using the xen clocksource instead of its
own clock ticks. In practice, this seems to be the cause of
infrequent lockups under load (and/or problems with suspending). A
workaround is to decouple the clock in the domU from the dom0:In your dom0 and domU /etc/sysctl.conf add the line:
xen.independent_wallclock=1. On the dom0, edit the configuration
file of the domU (e.g. /etc/xen/foobar.cfg and add (or expand) the
extra-line: extra="clocksource=jiffies".These settings can be activated without rebooting the domU. After
editing the configuration files, issue sysctl -p and echo "jiffies">
/sys/devices/system/clocksource/clocksource0/current_clocksource on
the domU prompt.Because the clock won't be relying on the dom0 clock anymore, you
probably need to use ntp on the domU to synchronize it properly to
the world.Hope this helps.
Thierry.
PGNet Dev a écrit :
hi,
On Mon, Oct 5, 2009 at 4:02 PM, Timo Sirainen <tss@iki.fi> wrote:
And no ntpd in your DomU?
nope.
service ntp status Checking for network time protocol daemon (NTPD): unused
any suggestions as to what/how to fix?
If no one here can give you a good answer, I'd try some Xen mailing list. I'm sure a lot of people are running Dovecot in Xen without time problems. If you do find out the problem, please let us know also.
i've been poring over the lists ... found nothing yet :-/