"AlwaysOn" is one of the most important features introduced in SQL Server 2012 .
It enables grouping of databases on a SQL server instance into "Availability Groups", and duplicating the whole Availability group of databases, onto up to 4 additional SQL Servers instances, All duplicated databases are readable. AlwaysOn relies on Windows Cluster which does not require a shared storage, and enables the failover of the whole Availability group onto another SQL Server Instance on another Node.
