Adding 2nd Exchange 2010 Server in Same Site

We're adding a 2nd Exchange 2010 server in our main office.  In the past I've just added a new server, moved everything to the new one, and decommissioned the old one.  This time I want to keep both servers and split our databases up between them.

I've attempted some research on this but I keep ending up seeing CAS arrays and DAGs but I'm not sure we need those since they seem to be more than I'm looking for.

1) OWA and Activesync.  Will the servers just magically know how to handle this or will I need to configure?  For example, someone connects to OWA which goes to the new server, but their mailbox is on a different server, will the first server automatically know how to proxy that connection?  Exchange does seem to magically know how to route things I've found.

2) Should I/Can I leave the CAS role on the old server?  Remove it?  Does it matter?

I'm just not sure I'm searching the right terms to find the info I need.
Tofu4679Asked:
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MASEE Solution Guide - Technical Dept HeadCommented:
Can you explain the purpose of having the 2nd exchange it will help us to propose you a better solution.

-->1) OWA and Activesync.  Will the servers just magically know how to handle this or will I need to configure?  For example, someone connects to OWA which goes to the new server, but their mailbox is on a different server, will the first server automatically know how to proxy that connection?  Exchange does seem to magically know how to route things I've found.
Exchange2010 is smart enough to find mailbox and proxy the traffic between each other.

-->2) Should I/Can I leave the CAS role on the old server?  Remove it?  Does it matter?
That depends on your requirment. If you have a CAS array in place your CAS server will be a member of the CAS array automatic.
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Tofu4679Author Commented:
Adding the 2nd server to split up the database load between them, not redundancy or anything.

We don't currently have a CAS array.
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tigermattCommented:
I've attempted some research on this but I keep ending up seeing CAS arrays and DAGs but I'm not sure we need those since they seem to be more than I'm looking for.
Depends on your end goal. A Database Availability Group ("DAG") provides highly available, fault tolerant mailbox storage; data replicated among multiple machines such that partial hardware (or software) failure should not render your mail environment offline. You would need sufficient storage provision on each member of the DAG to store all the replicated mail; sounds like you are not doing this. With multiple servers and the relatively cheap cost of storage, it might be worth considering, but that's up to organisational requirements and constraints... :-)

A CAS array object does not provide load balancing. It merely provides a virtual hostname for Outlook to use to connect to the CAS for mailbox data, providing a level of indirection via the DNS so that the physical server names are not hard-coded into Outlook profiles. It provides some additional flexibility for moving servers around, dropping new systems in and out without having to worry as much about client side configuration.
HOWEVER, you can combine a CAS array object with a load balancer; if the CAS array name points to the VIP of a load balancer, and the load balancer is configured to distribute traffic among two or more CAS servers, then load balancing of client access traffic is achieved -- care must be taken over traffic affinity and such.

OWA and Activesync.  Will the servers just magically know how to handle this or will I need to configure?  For example, someone connects to OWA which goes to the new server, but their mailbox is on a different server, will the first server automatically know how to proxy that connection?  Exchange does seem to magically know how to route things I've found.
Exchange "magically knows" how this works based on (a) which roles are installed on which servers, (b) the sites the mailbox data and CAS roles are located in (e.g. all the same site vs different sites) and (c) the values configured on the "InternalURL" and "ExternalURL" parameters of the various virtual directories.

In your case, with all servers in the same site and only a single CAS, this should indeed "just work". The description at TechNet has about as much information as you probably ever need.

Should I/Can I leave the CAS role on the old server?  Remove it?  Does it matter?
Depends on what you want to achieve. If you were going for high availability (i.e. with a DAG), you would be looking at rolling out multiple CAS roles behind a load balancer to ensure Client Access doesn't fail when a single server fails.

Since you don't seem to be doing that, it doesn't really matter; if the server hosting your CAS role fails, you'll lose all client access to mailbox data (even if the working mailbox server is up). If you want multiple CAS boxes, you need a method of getting the traffic to them, e.g. a load balancer. Windows NLB can be used as a poor man's load balancer, but it isn't recommended.
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AmitIT ArchitectCommented:
Just install second server and use it. Nothing more required. If you are looking for Exchange High Availability, then that require lot of planning and other tools, like a Load balancer. It is good to have DAG for Mailbox DB HA. Hub is automatically a HA feature, condition you need to have more than one Hub server. For CAS, you need HLB. CAS itself doesn't have any HA feature.

Let me know, if you need any designing help.
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Will SzymkowskiSenior Solution ArchitectCommented:
OWA and Activesync.  Will the servers just magically know how to handle this or will I need to configure?
No this will not configure itself. For internal access the default servername url's will be present however you will need to configure all of the external URL's.

As stated you will also need to have a CAS Array for each Active Directory Site where Exchange is being hosted. You will still require a load balancing solution as a CAS Array is not a load balancing mechanism in itself. It would be preferred to use a hardware load balancer.

The only role that is redundant in Exchange without having to do anything is the Hub Transport Role. A side from that all other roles require some configuration to actually become redundant.

So for CAS I would highly recommend you create a CAS Array and also load balancing as well, if you choose to install this role as well. If you simply do not have a load balancing solution in place for CAS, active directory will look and see that you have 2 CAS servers and it will send requests to both, which might seem fine.

The issue happens when you have one of your servers go offline. Active Directory will continue to send requests to both CAS servers becasue AD does not know that the server is off or not reachable. This is where it causes issues because users will start to get error messages because they are trying to connect to a CAS servers that is not reachable. This is where load balancing comes into play.

Should I/Can I leave the CAS role on the old server?
Yes you can leave it as is, but if you add the CAS role to the new Exchange server and you plan on keeping both then you need to have them load balanced.

You do not have to use DAG if you do not want to but your databases will not be redundant. OWA will proxy connections accordingly as well even to the new mailbox server.

Will.
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MASEE Solution Guide - Technical Dept HeadCommented:
If you dont have CAS array and if the first server fails your whole organization mailboxes will be offline.
Apart from that CAS array will not load balance by itself. You need a load balancer.

I suggest you create a CAS array and configure DAG. So you can manage by DNS Roundrobin which is not a autoamtic failover system. You will have to delete the failed CAS server entry from DNS.
FYI it is recommended to create CAS array even if you have only one CAS server.
http://blogs.technet.com/b/exchange/archive/2012/03/23/demystifying-the-cas-array-object-part-1.aspx

Please check this regarding DNS Roundrobin
http://www.experts-exchange.com/Software/Server_Software/Email_Servers/Exchange/Q_26819901.html
http://smtp25.blogspot.com/2012/01/exchange-2010-cas-array-simple-dns.html
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Hello WorldCommented:
Hi,

Are you want to deploy DAG in your environment?
As MAS mentioned, Exchange server will auto implement proxy basic on the mailbox database. More details about Exchange proxy and redirection, for your reference: https://technet.microsoft.com/en-us/library/bb310763(v=exchg.141).aspx

Windows Failover can't both apply for CAS Array and DAG, therefore the server with CAS role and MBX role can only  be a member of DAG or CAS Array.
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tigermattCommented:
No this will not configure itself. For internal access the default servername url's will be present however you will need to configure all of the external URL's.
If they only have a single CAS then there's no configuration to do; the CAS will run RPC calls to the mailbox server to retrieve the data.

It only becomes a problem if deploying multiple CAS.
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Will SzymkowskiSenior Solution ArchitectCommented:
@tigermatt, this was being implied if he was adding the CAS role to the second Exchange server he is bringing up. This would mean he would have 2 CAS servers in his environment. Which would lead him to have to configure the virtual directories on the new CAS server to match the current one.

Having a CAS array should already be in place because even if there is only 1 CAS server in the AD site CAS Array is still recommended. That being said he still requires a load balancing solution.

Will.
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tigermattCommented:
Precisely. It's not clear what the intended action regarding the CAS role is.

A CAS array should ideally have been deployed when the environment was originally provisioned as a matter of course, although its omission is not technically incorrect.
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