Introducing AlwaysOn Availability Groups

AlwaysOn Availability Groups, introduced with the release of SQL Server 2012, are best described as enhanced database mirroring. It allows a set of user databases to failover automatically between different instances installed on separate servers; these are commonly known as replicas. Thus, it provides both high availability and disaster recovery, and applications that use these databases are automatically redirected; this minimizes the application downtime. From a disaster recovery perspective, multiple copies of the databases are maintained. So, if you have your AlwaysOn Availability Group replicas dispersed across different sites, then you can make use of the multiple database replicas for disaster recovery; if you lose one site, your database and its data are also stored safely on the other site or sites.