Create distributed availability group on failover cluster instances

Hi,

 

I know from documentation that we can add two separate SQL Failover Clusters in a distributed SQL AlwaysOn Availability group, my questions are as follows:

• Do we need to change all SQL FCI DBs recovery mode to Full as normal SQL AlwaysOn Availability Group?
• Is there any specific requirements or considerations other than Single AD Domain for both SQL FCI, and open only SQL Instances Ports, and 5022?

Regards,

Maged