SQL Failover Clustering with Availability Groups: Single or Multiple Databases

Question

Company wants to implement AlwaysOn SQL Failover Clustering with Availability Groups, for server level and data protection.

Are arrangements below, only possible if 1 database is on the server, or could I have multiple databases below in arrangement?

Note: First picture has 4 servers,

Second picture only has 3 failover servers. Both have availability groups.

Answer 1

Are arrangements below, only possible if 1 database is on the server, or could I have multiple databases below in arrangement?

You can have as many databases as your hardware will support which depends on workload, server size, and other general infrastructure items such as latency and bandwidth of the connections.

I've witnessed AGs that are ~20TB in size across 4 databases, AGs that had over 1,100 databases, and all values in between. Completely depends on your workload, hardware, and what you'd like to accomplish.

Answer 2

Unless you are using Basic Availability Groups with Standard Edition, you can have multiple databases in an single AG.

Basic Availability Groups in Standard Edition have limitation of one database per AG.

https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/basic-availability-groups-always-on-availability-groups#limitations