You are evaluating the implementation of database availability groups (DAGs). You need to recommend a DAG implementation that meets the redundancy requirements of Fabrikam. What should you recommend?

Question

Options

• AAdd one Mailbox server to each site.
• BAdd one Mailbox server to each site.
• CAdd two Mailbox servers to each site.
• DAdd two Mailbox servers to each site.

• A
  14% (3)
• B
  5% (1)
• C
  9% (2)
• D
  73% (16)

Explanation

You need 2 DAGs to keep site resilience and to service the active population at each site during Using Multiple Database Availability Groups for Site Resilience In the preceding example, a single DAG extends across multiple datacenters, providing site resilience for either or both datacenters. When using a single DAG to provide site resilience in an environment where each datacenter to which you extend the DAG has an active user population, there is a single point of failure in the wide area network (WAN) connection. This is because quorum requires a majority of the voters to be active and able to communicate with each other. In the preceding example, the majority of voters are located in the Redmond datacenter. If the Dublin datacenter hosts active mailbox databases, and it has a local user population, a WAN outage would result in a messaging service outage for the Dublin users. When WAN connectivity breaks, only the DAG members in the Redmond datacenter retain quorum and continue providing messaging service. To eliminate the WAN as a single point of failure when you need to provide site resilience for multiple datacenters that each have an active user population, you should deploy multiple DAGs, where each DAG has a majority of voters in a separate datacenter. When a WAN outage occurs, replication will be blocked until connectivity is restored. Users will have messaging service, because each DAG continues to service its local user population.

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