In addition to normal IT best practices and redundant hardware, the DAG is the primary high-availability option for Exchange 2010 Mailbox servers. A DAG is a collection of servers that provides continuous replication and availability for mailbox databases, as shown in Figure 11-1.
Figure 11-1. A Database Availability Group
Continuous replication creates a passive database copy on another Mailbox server in the DAG, and then uses asynchronous log shipping to maintain the copies.
The continuous replication process follows these steps:
The active transaction log is written and then closed.
The Microsoft Exchange ...