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Implementing DAG in two site configuration

Posted on 2010-11-11
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Last Modified: 2012-05-10
OK so we currently have 2 active sites (A&B) with an Exchange 2010 SP1 server at each site, with users accessing both and are looking to implement DAG's. We also have a 3rd site (C) that is used for hosting our spam appliances and intranet servers. All sites are connected via a WAN, in the same AD domain and each site is in it's own AD Site.

My main concern with implementing DAG's in this configuration is what happens if I lose WAN connectivity?

I've read that SP1 now supports this type of configuration and helps prevent the potential 'split-brain' situation through the use of DAC (Datacenter Activation Coordination)

I have questions though.

Where should I place my primary FSW?
Should I configure an Alternate FileShareWitness server?

Example: Could I have Site A + FSW and Site B + AltFSW? What would happen if I lost WAN connectivity?

In the future we plan to implement a 4th site with an Exchange server.
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Question by:Jaws03
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Expert Comment

by:Akhater
ID: 34118332
>> My main concern with implementing DAG's in this configuration is what happens if I lose WAN connectivity?

the site with no file share witness will go down due to loss of quorum

>> I've read that SP1 now supports this type of configuration and helps prevent the potential 'split-brain' situation through the use of DAC (Datacenter Activation Coordination)

it does but wan connectivity issues are still not supported

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Author Comment

by:Jaws03
ID: 34139236
>> >> My main concern with implementing DAG's in this configuration is what happens if I lose WAN connectivity?

>>the site with no file share witness will go down due to loss of quorum


What would happen if I had an alternate file share witness at the other site?
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Expert Comment

by:Akhater
ID: 34140549
the concept of the alternate share witness is totally different, it is used only one you do a datacenter failover it is not for these scenarios

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Author Comment

by:Jaws03
ID: 34141079
So if WAN connectivity is lost all the users at the site with no FSW will not be able to access email even thought they have a functioning email server in the same location as them? Seems kind of limited?
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Akhater earned 500 total points
ID: 34141099
>> So if WAN connectivity is lost all the users at the site with no FSW will not be able to access email even thought they have a functioning email server in the same location as them?

exactly

>> Seems kind of limited?

DAG cross site was designed to be in a DR site as active/passive model and not as active/active. It could be better I know, hopefully exchange 2013 :)
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Author Closing Comment

by:Jaws03
ID: 34149846
NO
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Expert Comment

by:Akhater
ID: 34152820
@Jaws03 I am sorry but what do you mean by "NO" and why was this graded a B ? what was wrong in my answer ?
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