Definition

database availability group (DAG)

A database availability group (DAG) is a high availability (HA) and data recovery feature of Exchange Server 2010. 

A database availability group, which can consist of up to 16 Exchange mailbox servers, automates recovery at the database-level after a database, server or network failure. 

Database availability groups replaced Exchange Server 2007’s high-availability model, which was based on local continuous replication (LCR), standby continuous replication (SCR), single copy clustering (SCC) and cluster continuous replication (CCR).

Exchange administrators can choose to use DAGs in different geographic locations and in many different architectural designs and configurations, making it considerably more flexible than previous high-availability setups.

NTFAQGuy explains how high availability features have evolved from Exchange Server 2003 through Exchange Server 2010 and at 4 minutes in, explains how Exchange database availability groups work.

Contributor(s): Matt Gervais
This was last updated in July 2012
Posted by: Margaret Rouse

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