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DAG 2010 down after witness and DAG 1 out

Posted on 2013-11-11
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Last Modified: 2013-11-11
Hi folks,

I've made a DR test last week with our DAG system and found out that nothing worked as expected.

The sites are set as following
site A / 1 DAG & 1 Witness
site B / DR site with 1 DAG

When site A was totally shutdown (DAG1 & Witness), DAG of site B appeared as dismounted and couldn't work anymore.

What would be the best practice in this case to keep everything working in case of site A full down? Simply add an additionnal Witness server in Site B?

Please advise experts.
Regards,
David
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Question by:David_Pazos
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Expert Comment

by:iradatsiddiqui
ID: 39638654
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by:smithandandersen
smithandandersen earned 150 total points
ID: 39638659
you have to have a witness server in both locations
I had the exact same issue. Via support from MS exchange team a 2nd witness server was setup. Next time the server had issues the DAG responded as by design
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Author Comment

by:David_Pazos
ID: 39638764
Thanks for your replies. @smithandandersen, can you give me more details about that?

I've just read the following articles and it doesn't seems to be so automatically handled by DAG. Does anyone have made tests? Any tips on the configuration??

Add second witness with DAC?

http://clintboessen.blogspot.ch/2011/06/alternate-witness-server-in-database.html

http://technet.microsoft.com/en-us/library/dd351049.aspx

David
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by:Amit
Amit earned 150 total points
ID: 39638818
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Author Comment

by:David_Pazos
ID: 39638878
Thanks for this nice post. I still a bit confused for my setup

so if I resume with this scheme :
site A
main DC
DAG #1
Witness

site B
DC bkp
DAG #2

I should only add an additionnal Witness on site B without any Datacenter Activation Coordination Mode, right? What are your personal experiences? Thanks for sharing
David
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Accepted Solution

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mattclarified earned 200 total points
ID: 39638895
Hi,

You will need to run the following command on the primary DAG server

Set-DatabaseAvailabilityGroup -Identity DAG1 -AlternateWitnessDirectory C:\DAGFileShareWitnesses\DAG1.contoso.com -AlternateWitnessServer CAS3

Open in new window


You will also need to make sure that the ports for SMB are open between the exchange servers and both witness servers.

M@
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Author Comment

by:David_Pazos
ID: 39638954
Ok so not even needed to reinstall an Exchange server for this in DR site but just a server with a shared folder right? :)
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Expert Comment

by:mattclarified
ID: 39638989
Hi,

No you won't have to add another exchange server. You shouldn't even need to create the directory, I would use your secondary DC as the witness server and use the DAG command above to create a new share on it.

M@
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Expert Comment

by:mattclarified
ID: 39638994
If you do have to create the folder (sometimes it doesnt like to do it itself!), make sure you add full control permissions for the DAG's AD computer account.

M@
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Author Comment

by:David_Pazos
ID: 39639306
nice thx!!!

if someone needs the trick to add it on DC such right :
http://briandagan.com/how-to-add-a-domain-group-to-the-local-admini
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