Saturday, July 26, 2014

Exchange 2010 (SP3) - Migration - Part 3 - CAS Array

I already presented the CAS Array in a previous blog post, as well as some references to other sources:

As mentioned in that post, there is really no reason to specify "Exchange 2010 CAS Array" since the CAS Array does not exist in any other version of Exchange.

Moreover, the CAS Array is not specific to a migration. It could be configured for a new Exchange installation ("green field") as well.

Even so, I mention it here because it is a "Best Practices" step for most Exchange implementations. Yes, we could use Exchange without a CAS Array. Indeed, when there is only one Exchange server, the CAS Array provides no additional functionality. On the other hand, if we want high availability or load balancing, the CAS Array can be a crucial element. Even if we only have one Exchange server, it can be useful to create a CAS Array all the same, since it can facilitate the addition of another Client Access server, or the migration to a new CAS.

So, without repeating all of the previous post referenced above, I'll present the two steps of the creation of a CAS Array below.

First, we create the array (which is simply an object in Active Directory and not a physical or virtual device) with the following cmdlet:

[PS] C:\>New-ClientAccessArray -Name CAS-ARRAY-1 -Fqdn cas-array-1.mynet.lan -Site Default-First-Site-Name

As you can see, we need to specify the name, FQDN and the site of the CAS Array. Unlike Database Availability Groups (DAGs) for the Mailbox Role, a CAS Array cannot span two or more Active Directory sites (one CAS Array per site).

Then, in the DNS Management Console, or with dnscmd at the command line, we associate the CAS Array's FQDN with an IP address:

PS C:\> dnscmd dc2.mynet.lan /recordadd mynet.lan cas-array-1 A

At this point, the IP address is that of the first Exchange 2010 server that I have installed. As soon as I have my load balancer configured, I will associate the CAS Array FQDN with the virtual IP (VIP) or the load balancer.

If I only intend to have one CAS (at least for the time being), I would leave the CAS Array FQDN associated with the IP address of that server.

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