I've put questions here before about this but I'm still not quite getting it.
I have a single server now running Ex2010 in a lab. It's functioning as a real valid mail server, using a real test domain that I created.
I want to implement DAG's because, as I understand it, it will give me real-time database copies of my mailbox database.
So, that means I need to install a second server, join it to the domain and install Exchange 2010 on it.
The first question is: do I only need to install the Mailbox role on the second server in order to implement DAG's? I think this is true from what I've seen.
The second question is: Can I install also the HUB Transport and CA roles on this second physical box? The reason I'd want to do that would be to have a High Availability solution in place in the event my first Exchange box failed for some reason.
So this leads me to question 3 -- can I have a HA solution for Ex2010 with just two servers? I remember reading someplace that Microsoft recommends 3 servers at a minimum.
If I can't have HA with just two servers, but I can set up DAG's with just two servers, what would I have to do in the event Exchange server 1 went down? Would the DAG's automagically redirect to Exchange server 2 or would I need to intervene to make this happen?