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[Xen-users] "Time went backwards" issue

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Subject: [Xen-users] "Time went backwards" issue
From: Aleix Dorca <adorca@xxxxxx>
Date: Sat, 28 Feb 2009 07:32:44 +0100
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I've been running 8 Xen machines for about 9 months now (Ubuntu 8.04 LTS DomU and Xen 3.3.0).

I've been migrating since all previous services that ran on low-budget machines into brand new PowerEdge 1950 III Dell servers. Till last week I still had some Windows services to migrate. When I did, the xen machine running them hanged and crashed.

This was a complete surprise because all other xen's (same configurations and hardware) had NEVER failed at all. After looking at the logs I found the misterious "Time went backwards" issue that has been discusses little on this list. I had like fifteen "errors" in a half hour period.

I restarted the machine on thuesday and has been working fine since (almost a week), but the ocassional (once or twice per day) "Time went backawards" still appears but doesn't hang the computer.

This issue only happens on the xen machine that run Windows HVM domU's, and never happens on Xen with PV domU. Quite strange.

Now the questions: Should I use the "clockwall=1" on all windows HVM xen machines? Should I change from xen to jiffies clocksource? Upgrading to 3.3.1 will help? Maybe changing the Dom0 kernel? (Debian Lenny?)

Thanks a lot guys, this is really keeping me awake!


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