Because the Mailbox servers are configured with dual interfaces it is important to make sure that the secondary interface is not configured to register itself in DNS.
Open the TCP/IPv4 properties for the secondary interface one each server, click the Advanced button, navigate to the DNS tab and untick Register this connection's address in DNS.
Microsoft Exchange Server 2010 introduced a new high availability feature called the Database Availability Group (DAG).
This tutorial describes how Database Availability Groups work in Exchange Server 2010, as well as demonstrating the steps for deploying a DAG using Exchange Server 2010 SP1 and Windows Server 2008 R2.
A Database Availability Group is a group of up to 16 Exchange Server 2010 servers that are installed with the Mailbox server role.
In Exchange Server 2010 SP1 file mode replication is used to bring mailbox database copies into sync with each other (eg during the initial sync process when a new database copy is added).
Click the Manage button to commence adding the Mailbox servers to the DAG.
This involves installation and configuration of Windows Failover Clustering on the servers, so it can take a few minutes to finish.
This means that any given Mailbox server in the DAG can host all, some or none of the active mailbox copies at any given time.
This capability provides two immediate advantages over previous clustering models: Because the Database Availability Group utilizes an underlying Windows Failover Cluster the concept of quorum applies.
In Exchange Server 2010 RTM “file mode” replication is used.