I have already spoken about other high availability technologies like Log-Shipping, Database Mirroring, and Failover Clustering. I also spoke about Always On Availability groups briefly in the SQL 2016 new features post. Microsoft introduced SQL Server Always On Availability Groups in SQL Server 2012, which combined all the benefits of the three major High Availability techniques, i.e. Log-shipping, Mirroring & Failover Cluster.
In this post, I would talk about Always On Availability Groups in general and its benefits. Let’s have a look at what Availability Groups provide us:
–Total of 4 secondaries (2 Sync and 2 Async for 2012)
– Increased to 2 Sync and 6 Async in SQL Server 2014
–2 synchronous secondaries for both SQL 2012 and 2014
SQL Server 2014 also introduced “Add Azure Replica Wizard”
–Backup from Secondary
–Read-Intent Queries can be offloaded to Secondary Servers.
–Improves primary server performance by offloading work to secondary
The only negative to Always On Availability Groups is that it was an Enterprise Feature till SQL Server 2014.
With the introduction of a basic Availability Group functionality in SQL Server 2016, and deprecating Database Mirroring, this feature has become second to none as far as implementation is concerned.
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