We are thinking about setting up a DAG consisting of two Exchange machines, with one of them being located off-site with a decent WAN connection. We planned to have one of the serves at the main facility take over the witness role. The main goal is to be able to switch to the remote site in case the main server/network goes down, instead of using the other machine actively (unless that would be better).
With 2 servers down (out of 3), will the DAG even work if the main site goes down?
Will the switchover be automatic, or a manual process in that case?
And finally, how would the fall-back work (as I understand having 1 out of 3 DAG servers on-line will “break” DAG)?