Event 1090 FailoverClustering. The Cluster service cannot be started. An attempt to read configuration data from the Windows registry failed with error 2
The Cluster service cannot be started. An attempt to read configuration data from the Windows registry failed with error '2'. Please use the Failover Cluster Management snap-in to ensure that this machine is a member of a cluster. If you intend to add this machine to an existing cluster use the Add Node Wizard. Alternatively, if this machine has been configured as a member of a cluster, it will be necessary to restore the missing configuration data that is necessary for the Cluster Service to identify that it is a member of a cluster. Perform a System State Restore of this machine in order to restore the configuration data.
The cluster service fails
You are unable to View the cluster in the Failover Cluster Manager
All Databases are dismounted
You cannot start/uninstall the Cluster service
Open PowerShell as administrator and type the following command:
Remove-DatabaseAvailabilityGroupServer -MailboxServer <ServerName> -Identity <DAGName> -ConfigurationOnly
Now go back to EMC.
Open up Mailbox under Organization Configuration
Click the Database Availability Groups tab
The Member server field should be blank, if not, hit refresh
You will now be able to delete the DAG and mount the databases.