In an organisation I found the following setup:
Six VMs SQL1 to SQL6 in the same domain, each host two instances. They are in four AG groups, each AG contains 10-20 databases.
SQL1\INS1, SQL3\INS1, SQL5\INS1
SQL1\INS2, SQL3\INS2, SQL5\INS2
SQL2\INS3, SQL4\INS3, SQL6\INS3
SQL2\INS4, SQL4\INS4, SQL6\INS4
However, all the AG groups and all the servers are in one Windows failover cluster CLUS1. SQL5 and SQL6 are in DR data center so they don't have quorum vote. Quorum Modes is Node and File Share Majority.
I would like to hear your opinions and pros/cons to have all AG groups and servers/nodes in one cluster (license cost, perfromance, high availability and etc.)
* They don't use Failover Cluster Instance of SQL Server. Only AG groups and Windows Server Failover Cluster.