I have some concerns over my understanding of SQL Server Always On. Kindly can you correct me (conceptually) where needed:
Always On Clustering and Always On Availability Groups are 2 separate concepts. Clustering is a HA solution and AG is a DR solution. Is the Always On Clustering same as Windows server clustering?
To create an Always On cluster - we have to launch the installer and choose the "New SQL Server failover cluster installation", then on every new node we need to launch the installer and choose "Add Node". The cluster (with many node) operates as a single unit in terms of IP address so applications point to only one IP and if there is instance crash, then the failover is handled by the Clustering technology and no application IP changes are needed. Also, the users/logins are in sync and will continue to work in case of failover. This does not protect against disk failure as all nodes share same disk.
Assuming we have an SQL Server instance already (say server A), then to create Always On Clustering for this we need to follow the same steps as above (create a new failover cluster installation) and then add Server A as a node. Right?
Assuming we have a fresh SQL Server instance (with no HA/DR) and are planning to configure only AG, then we first need to ensure that the "Failover clustering" windows feature is enabled on each participating node. Then right click on the SQL Server service and enable "Always on Availability Groups". Then on the server instance we create the AG and configure databases into the group(s). This ensures availability at database level, however if there is failover then logins wont work any more (orphaned). There is no shared disk and hence disk crash of primary server wont cause any issues for the secondary server database. Also, the client applications will be pointing to the Listener IP and the Listener will ensure that the appropriate working server is utilized by the applications. Right?
In above scenario, "Failover clustering" windows feature is enabled so is clustering a pre-requisite for AG? Is the concept of clustering in Point 2 and Point 4 the same.
If I wish to configure both HA/DR using Always On (AG) and Failover Clustering, then is best practice to follow Point 2 and then point 4 or the opposite way? Also, should we use both the virtual cluster name and Listener or either one if sufficient?
What is difference between "SQL Server failover cluster installation" and Windows clustering?