DAG - Exchange 2010 Scenario, 3 sites, 3 DAG Members?

Is this feasible in an Exchange 2010 Database Availability Group?  Just checking my logic before offering the solution to my supervisor.

Site A:
1 DAG member

Site B:
1 DAG member

Site C:
1 DAG Member

Site A hosts Active A, Passive B
Site B hosts Active B, Passive A
Site C hosts Passive A and B, no actives

Site B will also run email backups to tape using Symantec -- will need to be able to back up both the active and passive databases without changing their states.

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Are this 3 AD sites?
What about redundancy for the CAS and HUB servers?
Where are you going to place the FSW?
NAMEWITHELD12Author Commented:
There will be a CAS / Hub Transport server at each site, but no array b/c they will be three AD Sites, also physically separated by geography.  Sorry, not sure what FSW is?
File Share Witness, the share where you wish to place the majority node set quorum.
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BusbarSolutions ArchitectCommented:
out of the box, Yes. there are some issues you have to worry about
you will have to make sure that WAN is fine, design the FSW location and make sure to activate DAC.
more about site resiliencey http://technet.microsoft.com/en-us/library/dd638137.aspx
Internal client will use SCP (service Connection Point) when using Autodiscover. The SCP is set by default to the first CAS you install into the Environment.
BusbarSolutions ArchitectCommented:
one note to worry is that you have manual intervention here, since you will need to re-configure the autodiscover A record with the correct IP after a site failure.
NAMEWITHELD12Author Commented:
oic - this would be the DAG Quorum system?  I was under the impression that an odd number of DAG members didn't require an external FSW, so this would just be the primary DAG in the group?  I guess that would be at Site A..the vast majority of our users will have mailboxes in that site.
You will always need a FSW. In case where you have an aqual amount of votes the FSW will count as vote and provide the majority.
NAMEWITHELD12Author Commented:
There are going to be situations where Site A and Site B will lose their connectivity...in this case, I don't want Site A's mailboxes to become active in Site B's DAG member...but rather keep everything up, since there's no cross-access between the two sites aside from mail flow (which I'm assuming would queue at the HT at each site until access is restored).  If I don't specify a FSW, would this mean I could manually fail over the site if it's a 100% outage?  I'm able to VPN in to the Site B network if I lose connectivity completely with Site A in order to perform any needed commands.
Antonio VargasMicrosoft Senior Cloud ConsultantCommented:
A DAG is a Cluster Service. when you create a DAG you are installing the cluster services on that node, and therefore you will always need the FSW, which is nothing more than a shared folder on one server that functions as a cluster quorum disk. By default the FSW is installed on the hub transport server role but you can install it on another server. It's not recommended to create the FSW on one domain controller because the DAG user needs to be a local admin on the FSW machine, and if that machine is a DC it needs to be domain admin, which it's not reccomended. Your design is a good out of the box design. If you have HT and CAS in every sites be sure to define in every database the rpcclientaccessserver atribute pointing to the CAS of that site. If that site fails the database will failover and you will need to change that attribute, because the CAS server will also be down. Regarding HT he uses the one that's on his site so having one per site is enough to maintain business continuity.

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BusbarSolutions ArchitectCommented:
this is why there is a DAC the database activiation coordinator that will solve the problem, check my previos post.
Antonio VargasMicrosoft Senior Cloud ConsultantCommented:
You cannot create a DAG without specifing the FSW. If you dont want that databases from site A failover to site B why do you add a database copy on site B? dont do it. Add the DAG to the 3 servers like this:

Database A: 2 copies in site A and C. Active in site A and passive in site C
Database B: 2 copies in site B and C. Active in site B and passive in site C
use the activation preference parameter to choose which one should be preferentially active.
NAMEWITHELD12Author Commented:
When the two sites lose connectivity to each other, we don't want it to failover, but if our Site A office is struck by some sort of long-term power outage, or physically damaged in some way, we do want it to failover...Site B is a sort of 24 hour protected facility, and would act as our primary site for all apps, including Exchange, in the event of a catastrophic occurence..
BusbarSolutions ArchitectCommented:
understanding database activiation coordinator
NAMEWITHELD12Author Commented:
This is some great info from everybody, I'm going to try to award everyone some points, if I can figure it out...thanks to all :)
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