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Re: [Xen-users] Problem with timekeeping

  • To: xen-users@xxxxxxxxxxxxxxxxxxx
  • From: Andy Smith <andy@xxxxxxxxxxxxxx>
  • Date: Tue, 27 Feb 2007 07:45:18 +0000
  • Delivery-date: Mon, 26 Feb 2007 23:44:41 -0800
  • List-id: Xen user discussion <xen-users.lists.xensource.com>
  • Openpgp: id=BF15490B; url=http://strugglers.net/~andy/pubkey.asc

On Tue, Feb 27, 2007 at 08:22:52AM +0100, Ulrich Windl wrote:
> On 26 Feb 2007 at 15:21, Fridtjof Busse wrote:
> > I'm running Xen 3.0.4 on an AMD64 server and noticed a weird problem:
> > The time in the guest is 2 minutes ahead of the host's time. The dom0 is
> > synchronized via NTP and the domU has independent_wallclock=0.
> > Any idea what might cause this?
> > Or is the only way to fix this to use independent_wallclock=1 and use
> > NTP in the guest as well?
> Using independent clocks and NTP everywhere fixes the problem, but basically 
> running NTP in Dom0 only and slaved clocks SHOULD work (but it doesn't). At 
> least 
> with SLES10 x86_64 and a 4 CPU Opeteron.

This matches my experience.  I have never seen any explanation for
this beyond "you have crap hardware" which I reject because I see it
on every platform I run Xen, from home servers based on "gamer"
motherboards, through supermicro cheap rackmounts, to HP and Dell

Running ntp everywhere is the only way I can keep the clocks


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