Setting up a new DAG is not something to do on a whim, nor is it something that you should attempt unless you have sufficient knowledge of all of the technologies that are involved. These include:
Windows Server 2008 and Failover Clustering
Exchange hides most of the details of dealing with Windows Failover Clustering from the administrator when it builds and maintains a DAG and you should never have to look at the cluster details unless a problem occurs and you have to carry out some investigation to retrieve information, probably under the direction of Microsoft Support. Even so, it’s still a good idea to know the nature of the beast with which you are dealing, if only at a reasonably ...