The Always On Availability Groups (AGs) feature is a high-availability and disaster-recovery solution that maximizes the availability of a set of user databases for an enterprise data estate.
Always On AGs are SQL Server’s premier HA/DR technology.
Always On AGs consist of the following main components: (Windows + SQL)
(1) Availability Group - contains user database(s).
(2) Primary replica - principal SQL Server Instance.
(3) Secondary Replica(s) - failover target SQL Server Instance.
(4) Windows Server Failover Cluster - a group of independent servers that work together to increase the availability of applications and services.
(5) Listener - unique DNS name that serves as a virtual network name (VNN).
Here is a typical architecture design for a 3-node, multi data center infrastructure.
|
|
|
|
|
|