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What is AlwaysOn AG?
AlwaysOn Availability Groups is a database mirroring technique for Microsoft SQL Server that allows administrators to pull together a group of user databases that can fail over together. Traditional database mirroring in SQL Server was only for a single database.
What is SQL Ag cluster?
SQL Server AlwaysOn is a marketing term which refers to the high availability and disaster recovery solution introduced when SQL Server 2012 was launched. To be more specific, SQL Server AlwaysOn consists of two technologies: AlwaysOn Failover Clustering Instances (AlwaysOn FCI)
What is considered high-availability?
High Availability (HA) describes systems that are dependable enough to operate continuously without failing. They are well-tested and sometimes equipped with redundant components. High availability refers to those systems that offer a high level of operational performance and quality over a relevant time period.
What’s the difference between an AG and a FCI?
FCI is for HA scenarios. An AG synchronous secondary replica, co-located with the primary, is for HA scenarios. An AG asynchronous secondary replica, in a different datacenter, is for DR scenarios. Here is an example MS link discussing this.
What do AlwaysOn availability groups and failover instances do?
It does not require reconfiguration of the clients and applications associated with the Server instances during failovers. AlwaysOn Availability Group and AlwaysOn Failover Instance are the two provisions that enable the users to increase the availability of SQL Server instance.
How does AlwaysOn maximize the availability of databases?
It maximizes the availability of the databases belonging to an enterprise. It supports two databases-Primary and Secondary. While the primary database is a set of read and write primary databases, the secondary databases are the corresponding databases of one to eight sets associated with primary database.
Which is the best AlwaysOn cluster for SQL Server?
Enables users to configure availability replica for supporting one or both the active-secondary capabilities, as per the user’s requirement. SQL Server AlwaysOn Failover Cluster Instance or FCI, a substantial offering of AlwaysOn, provides high availability at the server-instance level by making use of Windows Server Failover Clustering.