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2 Node DAG with CAS / HT

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2 Node DAG with CAS / HT - 16.Aug.2010 12:39:43 PM   


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today we have discussed a interessting solution to fulfill a cheap Exchange 2010 deplyment with only two nodes.
I have found many hints on using a DAG to HA the mailboxdata, the ht will be self management through Exchange (outgoing mailflow).
The only point is, how to get the CAS HA? Some solutions tell, that the clsuter could be used to create a IP resource. This looks fine, i think. But there are some limitations, i have read regarding the public folder access in this solution. Is this true?
A second thought of me is, that the HT must also be configured with a cluster IP resource, because incoming mail will be routed from the firewall to a defined IP. To get this HA, i will also need to do it equal.

What do you think? Would be very happy if someone could help me on the ay.



< Message edited by Peterle -- 16.Aug.2010 12:41:34 PM >
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RE: 2 Node DAG with CAS / HT - 16.Aug.2010 2:12:35 PM   


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Joined: 20.Aug.2009
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Hello mate,

Your question is not clear, i understood like what i said below
You want to configure exchange 2010 in 2 box with high availability(HA) on all three roles.

simple answer is not possible without a third party load balancer.

You can have all three roles installed and configure the exchange 2010 in a DAG. But you still need to use the replication concept for Public Folder, because DAG will not support public folder database( http://www.exchangedictionary.com/index.php/Articles/database-availability-group-exch2010.html ).
And if you want to configure load balancing or HA on CAS servers, you should configure CAS array and use a third party NLB. This is because you can not have both failover cluster and load balacce cluster on a same box.

Hope this will give you some insights.


MCSA- Messaging,
MCTS- Exchange 2010,2007
MCTS - AD 2008

(in reply to Peterle)
Post #: 2
RE: 2 Node DAG with CAS / HT - 17.Aug.2010 2:46:23 AM   


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Thanks for your reply.

The idea is to create manual additional IP Ressources in the Windows cluster service which is installed with creating the DAG.

We see no other chance to acomplish high avilibility with only two nodes and without a hardware loadbalancer.

We have clients Outlook 2007, possible that the cas array will work to provide HA. But we must also have only one nic for receiving emails from the internet. The mailflow is: mx record -> external ip -> firewall nat -> hub transport. We have no chance to create a second mx ressource record on the internet, due to insufficient external ip adresses.

Would be happy, if someone could get me on the right way. Thanks.


(in reply to praveenbalan)
Post #: 3
RE: 2 Node DAG with CAS / HT - 19.Aug.2010 5:54:26 PM   


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No suggestions so far?

(in reply to Peterle)
Post #: 4
RE: 2 Node DAG with CAS / HT - 2.Sep.2010 9:02:15 AM   


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Without a second external IP, and no load balancer, the answer is no.  The lack of a second external IP for an additional MX record makes it definitionally impossible to acheive HA from the inbound message perspective, and while you could implement round robin DNS for the CAS for clients, that is a poor answer, as it will simply keep flipping between the IPs, regardless of the availability of the box.

Not every problem has a solution without adding resources...

(in reply to Peterle)
Post #: 5

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