With the release of SQL Server 2012, one of the big marketing pushes by Microsoft was the new AlwaysOn features that were a part of the release. However, as a part of this push, a lot of confusion has occurred where articles, blogs, tweets, and forum posts refer to AlwaysOn as if it were a feature, and this is not the case. AlwaysOn covers more than one feature, the primary two features being Availability Groups and Failover Clustering. Both of these are referred to in the Books Online as AlwaysOn Availability Groups and AlwaysOn Failover Cluster Instances. We’ve also had a number of debates about whether or not other features are “AlwaysOn” enhancements in SQL Server 2012, and the problem is that it depends on who at Microsoft you talk to what answer you get back.
Since AlwaysOn is the marketing brand for High Availability other features like partially contained databases (which help facilitate easy failover of Availability Groups), online index rebuilds with LOB support, support for server core installations, and adding non-null columns to tables, could also be considered to be AlwaysOn features, and in some of the pre-launch materials these were included in the AlwaysOn presentations with Availability Groups and Failover Cluster Instances. When we recorded the SQL Server 2012 Early Adoption Cookbook content for Microsoft, these features were intermixed into the AlwaysOn content as well. Whether you want to group those into AlwaysOn or not isn’t the point of this blog post. Even without those features, AlwaysOn is still not a feature on it’s own, so make sure that you refer to the features as features, and AlwaysOn as a general topic that covers multiple features.