Installation guide

Database Availability Group (DAG) for Exchange Server 2010 or later

DAG is a failover cluster solution providing high availability and site resilience. DAG uses the

combination of two continuous replication technologies found in Exchange 2007: Cluster Continuous

Replication and Standby Continuous Replication. DAG is a group of up to 16 Exchange Mailbox

servers. Any node can host a copy of mailbox database from any other node. Each node can host

passive and active database copies. Up to 16 copies of each database can be created.

8.2 How many agents are required for cluster data

backup and recovery?

For successful data backup and recovery of a cluster Agent for Exchange has to be installed on each

node of the Exchange cluster.

What happens with backup if the Agent for Exchange is not installed on all nodes?

If the Agent for Exchange is not installed on all cluster nodes (for example, the agent was manually

uninstalled from one of the cluster nodes):

 The backup task completes with a warning, if the data selected for backup is hosted on the node

with the Agent for Exchange installed.

 The backup task fails with error, if the data selected for backup is hosted on the node without

the Agent for Exchange installed.

8.3 Exchange clusters on a management server

Exchange clusters are browsed and managed in the same way as any individual Exchange servers (in

the Microsoft Exchange servers (p. 43) view of the management server).

You manage a cluster as a whole rather than as a set of nodes. When selecting the cluster data for

backup (or browsing cluster data in the Data view), the data is displayed as a single instance even if

multiple copies of the data are available within the cluster.