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Advice on setting up time server in hyper-v environment

Posted on 2010-09-03
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Our DCs are virtualised within a Win 2008 R2 Hyper-V environment on a network not connected to the internet.  
Does anyone have advice as to best practice for setting up time service?

Currently I manually correct the time on the PDC (virtual) and have group policy set so that all servers and computers look to this pdc to set their time.
I have disabled the Time Integration within HyperV settings - but I seem to have a problem when rebooting the physical host that the PDC is running on. Possibly because the host cannot find the DC when it first starts up, it seems to make up its own time which then pushes to the dc and all other servers.Not sure if the host is getting the time from the bios, which I do keep correcting - but seems to be trailing off quite fast.

In any event I want to prevent the PDC from changing time unless I expressly correct it - as a simple reboot of the host server means the time is changed on all desktops and servers to something up to an hour out!
Any help gratefully received
thanks
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Question by:itadminuk
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robbe earned 250 total points
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First of all you've done the right thing ot disable the time sync. The DC should be the time source for all clients in the network. Second of all you should configure the DC to sync with an ntp server. Here is some more information about that: http://support.microsoft.com/kb/816042

Last but not least: It's not a good idea to join the host in the domain if you are running the DC virtualized. You should consider adding a physical dc to the network if you need that. Otherwise just leave it in a workgroup. For testing purposes you may consider to make the hyper v host a Domain Controller as well.

Greetz,
Robin
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by:msmamji
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robbe is spot on with everything especially with regards to having the Host machine on workgroup when all you DCs are virtualized.

You are wondering why you are still having time sync on the DC VM, despite having disable time synchronization. That is because time synchronization that is done when the VM is started is not overriden by this feature. You must understand that Physical Machine have battery-controlled clock from which the machine gets the time when it starts. There is no such clock in a VM, so when the VM boots, it retrieves it initial time from the host regardless of this setting. This option only controls whether further synchronization will be done or not.

So its not the restart of the Host that is causing this, rather this is caused by the booting of the VM. It boots and takes the initial time from the host and therefore you need to reset the time on the DC. I would suggest Having the Physical DC and making it the PDC to avoid such issue.

Regards,
Shahid
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by:robbe
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itadminuk,

Did we answered your question or do you need some more information?

Greetz,
Robin
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by:itadminuk
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thanks guys for your quick responses. really really helpful. Robbe - I can't configure an ntp server as it's not connected to the network but it does look as though I am going to have to see why the physical host time keeps drifting off.
Also Shahid - that's really answers the question - I didn't realise that the vM would STILL take the time off the host even with integration turned off.
I am now going to investigate whether I can use a physical dc or take the host off the domain and into a workgroup.
thanks guys
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by:msmamji
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Can Say it with surety as I have read it in the book, "Mastering Microsoft Virtualization", Chapter 3, Page 104, Heading "Integration Services". Mentioning here for reference

Regards,
Shahid
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