Converting to a CAS Array - Exchange 2010

Hello Experts!

I'm in the process of creating a redundant Exchange environment. I currently have a single Exchange 2010 server with MBX, CAS, and HUB roles, which handles everything in my single site production environment.

My question is about implementing a CAS Array. I have four new servers configured, 2 CAS and 2 MBX. I'd like to convert the CAS servers to an array, but read that it will add all CAS servers at my site into the array. I'm pretty sure, this would have serious repercussions for our clients connecting to the single CAS server. How should I proceed at this point? I'd like to create my array, migrate existing databases from the single server into a DAG with the two other MBX servers, then remove the CAS role entirely from the single server.

Thank you!
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Simon Butler (Sembee)Connect With a Mentor ConsultantCommented:
You can change the datatabases to the CAS array at any time. You can do them all at the same time. However the clients will not use them.

Clients will not use the CAS array address until you repair the Outlook profile. There is no automated way to do this. Even moving the mailboxes will not force the update.

Therefore the approach I would use is to configure the RPC CAS array DNS entry right now. Point it at an existing server with the CAS role. Adjust the databases to use it.
Then whenever you touch a client for any reason, repair the profile so they are using the CAS array address.

When you have introduced the new CAS role holders, you can just adjust the DNS entry to point the new server. Clients that were changed will use it immediately with zero impact, and you can continue to update existing clients.

The moving of the mailboxes is a completely independant on the CAS array, as long as the new target databases are configured correctly.

AmitIT ArchitectCommented:
You need to setup CAS Array first and then set the -RPCClientAccessServer for existing db to CAS Array name. New db's will use CAS array by default. More to read here

No change required from client side.
jmichaelpalermo4Author Commented:
Thank you! Here's the big question: is it possible to move individual databases/mailboxes/domains over to the new setup instead of everyone?

Currently: One Exchange server, all roles (with 10 different databases)
Moving to: Six Exchange servers, distributed roles

We'd like to move the clients from the one Exchange server to the 'full featured' setup in a phased approach. Moving everyone at once is frightening!

Is this possible?

Thanks so much!
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AmitIT ArchitectCommented:
No issues it is one time command and you need to run at same time for existing db's and for new db's it is not required.

Are you using NLB or HLB for load balancing.
jmichaelpalermo4Author Commented:
Simon - wow! So you're saying that we can move the databases into the CAS array with zero client impact? Then, as we get to each client, we "repair" or recreate their Outlook profile causing them to point to the new CAS array?

...then, once all the clients are moved over to the new CAS array, we can discontinue the old single server?

One thing I'm not completely clear said, "When you have introduced the new CAS role holders, you can just adjust the DNS entry to point the new server." Our previous clients pointed directly to a server name (internal NETBIOS name). How do we adjust that name to point to the new CAS array? ...or is that not what you mean here?

Thanks again - this is sounding much better than I had originally anticipated!
Simon Butler (Sembee)Connect With a Mentor ConsultantCommented:
To change the name that the clients are using, that is what repairing the profile does.
Autodiscover will run, forcing a full update. As long as you have the CAS Array address in place and have adjusted the mailbox database then the clients will start using the new name.

The CAS Array address needs to an internal name only, it should not resolve on the internet and should not be used for anything other than the CAS array.

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