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Exchange 2010 site swicth over

Posted on 2014-02-06
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Last Modified: 2016-05-22
I have a 2010 exchange DAG  with DAC enabled. It is spread across two remote sites single AD forest with two AD servers in one site and two in the other. the configuration is 3 mailbox servers and one witness server in site 1 and 2 mailbox servers with an alternate witness server in site 2. I am trying to wrap my head around the votes in this configuration to keep site 2 up,
if I am correct in thinking?
In site1 3+1 =4 votes in site2 2+1=3 votes if I lost site one completely would site 2 crash completely because of to many votes are lost?
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Question by:Cecilpierce
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Expert Comment

by:Gareth Gudger
ID: 39840676
Site 1 technically does not need a Witness server. You only need a Witness Server when you have an even number of DAG  members. If you have an odd number, which you do, then you do not need it. A Witness Server is purely just a tiebreaker. So you could eliminate the Witness Server from site 1.

Are members in Site 2 in the same DAG? Are they configured as Passive, Lagged Copies? I assume all the active copies of databases are in Site 1?
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Author Comment

by:Cecilpierce
ID: 39840684
members in site 2 are in the same DAG they also hold 1 active database each and 1 passive copy of the other 4 databases
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Author Comment

by:Cecilpierce
ID: 39840750
as for the witness servers I should just remove the primary one in site one and make the one in site 2 primary witness?
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Simon Butler (Sembee) earned 500 total points
ID: 39841420
If everything is in a single DAG, then you cannot keep site 2 alive. Simple as that. Votes doesn't come in to it.
If the link fails then the servers in site 2 lose quorum. Anything else becomes a split brain scenario which must be avoided.

I will be blunt, the design is wrong and I fail to see how someone could have designed it to be in a single DAG.
As there are two sites with at least two servers in each site what should have been done is two separate DAGs, one for each site, with associated FSW. If you want off site replica, then deploy a six server deployment, with a passive in the other site. That passive can then be used for hub and CAS roles by the clients in the site.

Simon.
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Author Comment

by:Cecilpierce
ID: 39842045
so Simon you are saying if I open EMC and navigate to organization configuration and look in database availability groups I should see DAG1 and DAG2? currently I see DAG1 with 2 DAG networks
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Assisted Solution

by:Simon Butler (Sembee)
Simon Butler (Sembee) earned 500 total points
ID: 39842243
No, I am not saying you should see that, I am saying that is how it should have been configured. Basically the DAG needs a redesign.

Simon.
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Author Comment

by:Cecilpierce
ID: 39842306
Simon I have attached a picture of what I see can you explain to me what is wrong, then I will contact MS support and get this configured right. I knew something was not right!@
DAGNETWORK.png
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Author Comment

by:Cecilpierce
ID: 39842326
just so you know I also have 3 CAS in site 1 and 3 CAS in site 2
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Assisted Solution

by:Simon Butler (Sembee)
Simon Butler (Sembee) earned 500 total points
ID: 39842539
It isn't the DAG network that is wrong.
What you should have is two DAGs completely, one for each site.
You can use a CAS in each site as the FSW.

It will require some pretty extensive work to correct but at the moment if you want both sites to stay up in the event of a WAN failure you aren't going to get that.

The best practise now is to not split the roles out. Therefore if you have Exchange licences in use elsewhere for other roles you could look at a major redesign.

Simon.
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Author Comment

by:Cecilpierce
ID: 39877632
I am currently engaged with MS support, and they are running me thru the ringer as usual
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