Specifications

Best Practices for Virtualizing and Managing Exchange 2013
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ensures that even under contention, the Exchange 2013 virtual machine, upon failover, will successfully
start and receive the resources it needs to perform at the desired levels—taking resources from other
currently running virtual machines, if required.
Resilient Exchange Configuration on a Hyper-V Cluster
A Database Availability Group is the base component of the high availability and site resilience framework
built into Exchange 2013. A group of up to 16 Mailbox servers, a DAG hosts a set of databases and
provides automatic and database-level recovery from failures. Any server in a DAG can host a copy of a
mailbox database from any other server in the same DAG. When a server is added to a DAG, it works with
the other servers in the DAG to provide automatic recovery from failures that affect the mailbox
databases, such as a disk or server failure.
When two or more virtual machines running Exchange 2013 are configured as a DAG solution, one virtual
machine will take over if any of the others fails (Figure 35).
Figure 35: Exchange virtual machines running as a DAG solution across data centers