Restoring Virtualized Win2k8 DC from backup

Ok, we are backing up our VM DC's every 2 hours.  

Should we need to restore one from backup how long can AD be down for and will we experience problems should we restore from a 2hr backup?  Will take a minute to restore.

and

Should we lose a DC and not be restored within hours or days what is required to restore the DC?  I assume build a new VM and add as a DC and forcibly remove roles from AD?
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CHI-LTDAsked:
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Sarang TinguriaConnect With a Mentor Sr EngineerCommented:
You need to understand things here

If you restore the DC from image or snapshots then you may face USN rollback issue
To know more on USN rollback follow http://utools.com/help/UsnRollback.asp

It is allways a wise decision and standard practice to have minimum 2 DC's in Domain at a site
I would also prefer to have backup of system state too...It does not cost you anything than some disk space

If you have two DC's and one goes down you can start 2nd DC in 30 Mins thats't too without disrupting services
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Krzysztof PytkoConnect With a Mentor Senior Active Directory EngineerCommented:
You need to have at least 2 DCs then you don't have to worry about that. If one DC would go down then the other is serving AD services. Just remember that you cannot use restore from snapshot on your 2008 DC, the only allowed option is restore from "System State Backup" which requires new server to be installed and then you may restore it from System State

In case that yo  have more than 1 DC in your network and one of DCs would die, then you may simply do metadata cleanup of that DC and that's all

Regards,
Krzysztof
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Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
AD DCs used to be 60 days before tombstone, and it would not replicate, it's now 180 days by default.

build a new VM, promote to a DC (dcpromo), depending upon which has failed, sieze the FSMO roles, and remove the old DC from AD.
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CHI-LTDAuthor Commented:
We have 2x DC's at Site A and 2x at Site B (over a VPN).

So no need to backup then?  Using acronis...  Not sure what you mean by system state..
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Krzysztof PytkoConnect With a Mentor Senior Active Directory EngineerCommented:
You should have at least 2 DCs per Site for more security. If your replication does not work over VPN you would face AD DB missing updates. Mostly inter-site replication (remote locations - different sites) issues face domain environments than intra-site replication (local sites)

Krzysztof
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
I would recommend a Backup, just in case.
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Neil RussellConnect With a Mentor Technical Development LeadCommented:
Personally I dont back up DC's at all now. A restore of an AD VM is more hastle than its worth and can cause issues.
So long as you have multiple DC's, Shoot yourself if you dont, AND you restrict DC's to being just that, no additional applications running on them, no file stores on them, just plain simple AD and DNS/DHCP services.

Now should you lose a DC you just create a new one and as everyone else says, force any FSMO roles that your old one had and meta data clean up to get rid of old one.

A thing to consider is splitting your DHCP role amongst multiple servers and splitting your scopes between them for redundancy. You dont want to lose the only DC on a site with DHCP on it do you!?
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CHI-LTDAuthor Commented:
in case?
If it blue screens or someone deletes the VM, then restoring it a few hours later will be ok then?
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CHI-LTDAuthor Commented:
Yes, split DNS and DHCP...
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
yes, you can do that, restore.
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CHI-LTDAuthor Commented:
But as per neil, surely its at risk of causing issues with AD?
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CHI-LTDAuthor Commented:
What triggers the event ids and issues with AD?  The amount of time?  The amount of changes made within the database(s)?  Replication?

Not sure what you mean: If you have two DC's and one goes down you can start 2nd DC in 30 Mins thats't too without disrupting services
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Sarang TinguriaConnect With a Mentor Sr EngineerCommented:
I mean you have 2 DC's in same domain and at same site assuming that you have put IP of both DC's in client DNS search order

and your DC1 crashes then all login/authentication and group policies request will be processed by DC2

in meantime you can format the crashed DC and promote that as a new DC ..with clean installation ...
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CHI-LTDAuthor Commented:
So consensus is to back them up but in real world you wouldn't restore them, ever.  If failure occurs, build new DC, seize/transfer roles and clear old metadata from AD of failed DC?
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Sarang TinguriaSr EngineerCommented:
Yes but the backup is taken incase you have any rarest of the rare event when both of your DC's are down
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CHI-LTDAuthor Commented:
continuing with backups, every 2-3 hrs, but understand that if the dc fails that we probably wont restore from the backup, unless a last resort.
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