At the moment I have a single Exchange 2010 server with all roles (MB, HT & CAS).
I am looking to improve our email recovery time in the event of a disaster. I understand that true HA with site resiliency requires CAS arrays and hardware network balancing. Unfortunately this isn't something my company is willing to pay for. At the moment we just backup the mailbox databases daily with DPM2012 and would need rebuild an Exchange server at our secondary site if we were to lose out primary site (head office). This gives us an email recovery time of about 4-5 hours.
I've been looking at DAGs. Am I able to simply build a second Exchange 2010 server offsite (with MN/HT/CAS roles) and group them together in a single, two node DAG?
If so, in the event of a disaster where by I lost my primary server / site (EX1), would the second server (EX2) automatically mount the mailbox DB copies and it just be a matter of redirecting our MX records to this new server?
Edit: My current Exchange 2010 server in installed on Server 2008 R2 DataCentre