Peter_Channing
Contributor
Contributor

Snapshots and time sync issues

Looking for some insight on snapshots, in particular the effect on the OS time when a snapshot is removed.

My team manages a shared environment and we recently recieved concerns from one of our customers about time sync errors in the event logs of their Windows 2008 server. The server is not a DC but is running some time senstive database software.

Previously I do believe the time sync events have been recorded in event logs of other machines but because the other systems didnt have time sensitive applications running on them, the customer's havent noticed them.

Our Operations team has narrowed the time sync events down to the removal of snapshots, specifically when backups are finished and the snapshots are removed.

Can anyone confirm that this is a know issue or if it is something inherent to the snapshot procedure? Is there anythign we can do to mitigate the problem?

Oh, I forgot to mention that the these events occured on a machine that is set to sync its time with an internet source. VMware Tools is not configured for time sync with the host.

We will be opening a support call with VMware, but thought I would bounce the questions in the forums for some first hand experience.

Thanks in advance.

Peter

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3 Replies
a_p_
Leadership
Leadership

You may want to take a look at http://kb.vmware.com/kb/1189 to see how time sync for this (and other) events can be disabled.

André

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Andre443
Contributor
Contributor

Hi,

I have the same problem wiht the time sync guest VM when i take a snapshot.

In fact, after i take a snapshot the time offset become about 1 minutes.

The NTP in the server is configured with the domain controler NT5DS.

The sync time with Host and VMtools is uncheked and not configured in the VM.

I do not know where it can come.

Guest VM : Windows 2003 Server

vSphere 5.1


Thank you advance for your help.

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xHCx
Contributor
Contributor

Hi,

You observerd discrepancies while removing the snapshot - I would suggest to check whether the ESX host is synchronized with NTP, since the VM is synchronized to host time when certain operations like removing a snapshot are done.

Technical information on time in VMs:

http://www.vmware.com/files/pdf/techpaper/Timekeeping-In-VirtualMachines.pdf

I have the same issue while taking a snapshot as Andre, time difference is about one minute. I can observe how the clock gets a lag of 90 seconds while the snapshot is taken - at the end it is running in fast forward, but stopps when difference is reduced to 60 seconds. Any suggestions on that?

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