I am trying to set up a 2nd Exchange server for failover, I need high availability. Can I put mailbox/CAS/HT roles on each server and join them to a DAG? If I do this, can I run MLB on the DC both on the same LAN. Both exchange servers are in offices with DC's (2008r2 Standard) The DC's are fairly (Dell T420, less than a year old) robust and not being used for anything other than to house scans and DNS. Currently we are just running all Exchange roles on one server.