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Re: [Xen-users] Xen timekeeping best practices

On Fri, Apr 13, 2012 at 2:49 PM, Remi Gacogne <rgacogne-xen@xxxxxxxxxxxx> wrote:

Miles Fidelman wrote:
There's a pretty good discussion on the Debian Xen Wiki, at http://wiki.debian.org/Xen scroll down or search the page for the section starting: 'clocksource/0: Time went backwards' - which lists several workarounds note that some of them no longer work with Xen 4 (I think xen.independent_wallclock=1 is no longer recognized)

I second that. While it was possible to get a pretty accurate time in Xen 3 by using independent_wallclock, I have been unable to do so with Xen 4 so far.

We have several Xen 4.0.1 production servers, and even by using NTP in dom0 AND domU we have a recurring problem where the clock goes out of sync for an hour or so. Using NTP in each domU with the "disable kernel" option seems to help a bit, but for some users needing less than a few seconds of time drift it is a real issue.

I am currently thinking of downgrading some users to Xen 3 to work around this..

This is annoying, as I am on the verge of migrating production machines from Xen 3 to 4.
I am currently stuck because of time issues with the test machines I've already migrated. In our environnement 200 ms of time drift is unacceptable.

Has anybody had feedback from Xen development teams? Wondering what will it take in order to fix this issue...

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