You have a database availability group (DAG). The DAG is configured as shown in the following table.
You need to prevent a split-brain condition if a restore operation of the DAG occurs.
What should you do?
A. Deploy an alternate witness server to each site.
B. Modify the Datacenter Activation Coordination (DAC) mode.
C. Set the quorum model of the cluster to Node and Disk Majority.
D. Deploy another Mailbox server to Site2.
Correct Answer: B
Explanation/Reference:
Explanation:
Datacenter Activation Coordination (DAC) mode is a property setting for a database availability group (DAG). DAC mode is disabled by default and should be enabled for all DAGs with two or more members that use continuous replication.
If a catastrophic failure occurs that affects the DAG (for example, a complete failure of one of the datacenters), DAC mode is used to control the startup database mount behavior of a DAG. When DAC mode isn’t enabled and a failure occurs that affects multiple servers in the DAG, and then when a majority of the DAG members are restored after the failure, the DAG will restart and attempt to mount databases. In a multi-datacenter configuration, this behavior could cause split brain syndrome, a condition that occurs when all networks fail, and DAG members can’t receive heartbeat signals from each other. Split brain syndrome can also occur when network connectivity is severed between datacenters. Split brain syndrome is prevented by always requiring a majority of the DAG members (and in the case of DAGs with an even number of members, the DAG’s witness server) to be available and interacting for the DAG to be operational. When a majority of the members are communicating, the DAG is said to have quorum.
