Recently I had a VMware ESXi (4.1 and 5.0 are the same) environment and creating three VM server (Windows 2008 R2 Standard). I found a interesting thing is whenever I manually changed the ESXi host time a big value let's say 5mins or 10mins.

 

And roughly within one hour later, all three VMs have been changed the time, like "The system time has changed to ?2011?-?12?-?29T07:27:38.500000000Z from ?2011?-?12?-?29T07:22:41.502723100Z." EventID is 1, and user is "system". I checked everything with the w32time service inside the windows registry and disable all NTP, even disable w32time service. This one seems to happen again and again.

 

Then I enable the logging with w32time service and found the SyncToCmos is yes, I suspect the root cause is VM try to sync with hardware sometimes. Would like try to disable it and see how is going. Any idea with this kind of issue? Your reply will be greatly appreciated!

Hi,

 

This is a problem related to VMware... anyway... take a look at these 2 topics:

 

http://xtravirt.com/disabling-virtual-machine-guest-host-time-synchronization-multiple-hypervisors

 

http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1189

 

You CANNOT disable SyncToCmos manually, there's no option for that.

Thanks ICTCity, I did try that before I posted this topic, unfortunately it didn't solve my issue.