The official SQL Server AlwaysOn team blog.
One of the common questions we hear all the time is what are the requirements for setting up an Availability Group and how does that compare to database mirroring. I would like to answer this by going over a migration scenario.
Let's take a scenario where you
have a primary datacenter and a secondary datacenter. Your mission critical
application depends on 3 databases and all the databases are mirrored to the
secondary datacenter. In this configuration AlwaysOn-Srv2 is the principal SQL
Server instance and AlwaysOn-Srv7 is the mirror SQL Server instance. Both the
instances are standalone instances. The three databases are AlwaysonDb1, AlwaysonDb2 and AlwaysonDb3.
The mirror configuration currently is setup for high safety or synchronous mode.
The following video walks through the steps involved in migrating the database mirroring configuration to an availability group. In this video I'm using the CTP1 release, which only supports creating an availability group with a single asynchronous secondary. The walk through will go over the details of the pre-requisites of AlwaysOn Availability group and the steps involved in creating a new group.
There are a few things i want to recap here around the setup and clustering requirement