Add another Exchange Server to setup a DAG

I am looking to get some advice here on how to setup a DAG so have better availability for Exchange 2010 mailboxes.

I have in the environment:
2 x Virtual Win 2008 R2 systems (vmware/vsphere) running Exchange 2010
Both servers roles each have HUB, Client Access and Mailbox.
both have only a single network card (the virtual network card VMXNET3)
One of these mail servers has the pointing to it.

I currently don't have a CAS array.
Can I work with these 2 servers, assuming there is enough space, to establish a DAG between the two of them and have replication and higher availability?
Anything I need to change for them, or any new server I'd need to add into the mix?

Just looking for the best next steps to get something better going
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Amit KumarCommented:
As a best practice you will have to add one more NIC to each server to configure DAG. This NIC will be configured only for replication traffic, this NIC does not need a subnet which communicate to all clients. Both server should communicate to each other.

Now if you have DAG configured on servers which is having CAS role too so you can't configure NLB of CAS Servers to achieve HA of CAS. If you have decided to install CAS roles on same servers those are running with DAG so you will have to get Hardware load balancer. It will provide one DNS name with VIP which can be configured as CAS array on all DBs.  

HLB is sought of expensive solution, I would recommend if possible get 2 more servers and install CAS+HT on both then configure NLB on both nodes. So you will have 2 Mailbox servers with DAG and 2 servers with CAS + HT. In case one server failed e.g. Mailbox servers node so you have another node working and if one node failed from CAS+HT so another node will provide you services.

HT role can be collocated with MBX server because Hub server is much redundant if they are installed in multiple instances. But CAS roles should be installed on diff. server if you have configured DAG.
Simon Butler (Sembee)ConsultantCommented:
Which edition of Windows do you have? Standard or Enterprise?

If standard, then you cannot deploy a DAG. You would need to build a new machine with Enterprise edition of Windows 2008 R2 (or standard edition of Windows 2012), move all users to that new machine, then remove Exchange from the original one and rebuild it with the same OS as the first.
It is not supported to change the edition of Windows with Exchange installed.

I would create a CAS Array right now, and start going through the Outlook clients repairing the profile so that the clients are using the CAS Array address.

As for the recommendation above, I think that is a very poor recommendation.
Additional Windows and Exchange licences are a poor choice. Windows NLB is not recommended by the Exchange product team. If you take the cost of the additional licences you can get a virtual load balancer from either Kemp or Jetnexus for very similar money. That will give you a much better more reliable solution than Windows NLB, without additional servers to support. Depending on the number of users, the free load balancer from Kemp can by enough.

Additional NICs are not always the best option, particularly if you only a single NIC in the VM host. Large implementations maybe, but on smaller ones they add additional complexity for very little gain.


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garryshapeAuthor Commented:
Ok yes it is windows 2008 r2 enterprise
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garryshapeAuthor Commented:
If I create a CAS Array will that affect any existing connections where users' Exchange profiles are connecting directly to their mail server?
Simon Butler (Sembee)ConsultantCommented:
The creation of the CAS array has no effect on existing users because the end point they are using is still valid.
However if any Outlook profiles are repaired or created after creating it then they will use the CAS Array address instead. It is best practise to have a CAS Array on all deployments, no matter the size, to deal with this exact scenario. For something that takes less than five minutes to create it can avoid a lot of work.

garryshapeAuthor Commented:
Ok cool. yeah stinks it wasn't setup to begin with. Just acquired it so working backwards a bit on some things.

What's interesting is that this article demystifying-the-cas-array-object ( says it is not a load balancer but if you run the Help in Powershell on New-ClientAccessArray it says "Use the New-ClientAccessArray cmdlet to create an object that represents a load balanced array of Client Access servers within a single Active Directory site."

I understand at this point that the casarray dns entry would need to point to an actual NLB but is that what the description of the cmdlet is referring to
Simon Butler (Sembee)ConsultantCommented:
The key word is "represents". Think of it as a virtual Exchange server. It can point to a load balancer, but it can also point to a single server.

garryshapeAuthor Commented:
Ok great thank you

Any chance you know where in ADSI edit the "msExchServerSite" can be found for the Exchange servers? I'm not showing it on the actual mail servers object there, the property doesn't appear to exist.
Trying to confirm that the servers are in the same site according to ADSI
Simon Butler (Sembee)ConsultantCommented:
Never looked in ADSIEDIT for the information

get-exchangeserver | select identity, site

That will return the information that you need.

garryshapeAuthor Commented:
What would you recommend for a database naming convention of the database is going to be in a DAG?
Will Exchange 2010 do any auto mailbox moves to balance out the databases, thus rendering naming conventions for a specific department useless?
Or would doing something like database name "DAGStaff1" and "DAGStaff2" or "DAGIntern1" be proper if they respectively only hold mailboxes for people in those 'categories' if you will.

And would you recommend having the mail server name in the database naming convention?

Like MAIL2-DAG-Staff-1
Simon Butler (Sembee)ConsultantCommented:
Exchange doesn't do any kind of balancing of the databases, other than at the point of creation (IF you don't specify the database during the creation).
The database names are unique within the DAG - remember they don't belong to any particular server.

Therefore the most common I have used are

Mailbox Database x (where x is a number)
Location Mailbox Database x (where location is the region the servers are in, x is a number)
Role Mailbox Database (where role could also be a department etc).

I have never used the name "DAG" in the database name, unless there are multiple DAGs in a large implementation, then it could be something like Sales Database 1 DAG1.
I also don't use anything like "40mb Mailbox Database" where 40mb is the size of the attachments that can be used, or mailbox size maximum. Too much work.

Usual rule here - keep it very simple. Something that makes it obvious what it is if you are going to sort, if you are not, then a plain number convention.

garryshapeAuthor Commented:
I think I was considering DAG in naming convention for now because not every database will be in a a Database Availability Group
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