OK, if i have (2) Exchange 2010 SP1 boxes and both have CAS, HT and Mailbox roles and I've configured a DAG between the 2 and I've created a CAS array and both boxes are members. I want to know what is my best option for which IP address I should point the CAS array to? Remember, I don't have NLB or a hardware load balancer at this point (although I hope to procure/deploy a Kemp appliance in the future).
Right now the CAS array is named Outlook and I have an internal DNS record for Outlook that points to 1 of the 2010 boxes. I've set the TTL value to 5 minutes for this record. If I had a failure of this CAS I figured I could manually change the IP to that of the 2nd 2010 box. I've read that I could assign a 2nd DNS record for the CAS array and setup DNS Round Robin, but that could result in half of the users getting pointed to a failed device in the event of a failure - is this a better approach that what I currently have? Seems like half getting pointed to a failed device is better than all getting pointed to a failed device? If there was a failure, what should I do - just remove the DNS entry for the failed server or change it so they both point to the same box?
Or, I've seen a lot of recommendations to point the CAS array to the IP address of the DAG, this is where my uncertainty comes into play, what exactly is this achieving? Would this allow the clients to always be pointing to the live server in the event of a failure? Would this automatically send clients directly to the box that hosts their live mailbox (vs the other server that would host their passive mailbox)?
I've seen so many comments about all three of these options, but I haven't seen a detailed description and comparison of them all. And I'm looking for a clear understanding of what pointing the CAS array to the DAG IP will do.