[cvsnt] Virtual Machines
Peter.Crowther at melandra.com
Thu Dec 6 15:35:12 GMT 2007
> From: bwhicks at aep.com
> Is this an issue if your server is part of a domain (domain
> controller is
> on a physical box). It should sync with the domain controller fairly
> regularly, right?
Sync is variable, depending on how much the clock drifts (see http://www.microsoft.com/technet/prodtechnol/windowsserver2003/technologies/security/ws03mngd/26_s3wts.mspx for some of the gory details). That said, I've seen VMs where the clocks are 5% adrift - drifting by 3 seconds per minute. Even the lowest automated options for the Windows time service have issues dealing with that, as they simply can't move the clock by enough to keep up without manual registry tweaks. VMs can run fast, slow or on time, and it can vary with host system load. A swift Google (I used: virtual machine clock drift) should give you plenty of information on the topic. My VM's not the worst - there's at least one report out there (http://www.imacat.idv.tw/tech/vsntp.html) of a VM that's routinely 4 seconds per minute fast.
I may be raising a spectre that doesn't appear on your system, so test your VM - with the rest of the system under a variety of loads - before panicing. Also, Arthur says the authors routinely test using VMs, so presumably CVSNT is at least somewhat resilient to such problems and the resulting weirdness in system time as the various time services try to correct for the problem.
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