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Rick Heiges

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Basic Availability Groups in SQL Server 2016

Since SQL Server 2012, Database Mirroring (DBM) has been a deprecated feature meaning that it will be eventually removed in a future version of SQL Server.  It is still available in SQL Server 2016.  One of the best things about DBM is that it was a limited feature in Standard Edition since SQL Server 2005. The AG feature first introduced in SQL Server 2012 was the successor of DBM, but there were some details which prevented it from being offered at the Standard Edition level such as the requirement for Active Directory Domain security.

To address the eventual removal of DBM from SQL Server, Microsoft has created a new level of AG called a Basic Availability Group.  It is to be very similar to the pros/cons of DBM in Standard Edition today.  The following represent a summary of the new Basic AG:

-          Maximum of Two (2) Replicas (the Primary and one secondary)

-          One (1) database per AG

-          The Secondary Replica is not Active/Readable, but a Database Snapshot could still be utilized

-          Microsoft Clustering Services(MSCS) Required - No Witness – MSCS detects failover via quorum

Due to this new term of Basic Availability Group, the current term of Availability Group may also be referenced as Advanced Availability Group going forward.

One other difference between DBM and a Basic AG is that the Basic AG supports both Synchronous and Asynchronous modes.  DBM only supported Synchronous mode.  I believe the main reason for this change is to make it easier for the secondary replica to be in an Azure VM.  DBM is still in SQL Server 2016; I would have to believe that it will not be in the next release of SQL Server - whenever that is.

Here is another blog post about SQL Server 2016 Availability Groups.

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Published Thursday, January 21, 2016 2:07 PM by RickHeiges

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ChrisP said:

So are you saying that database snapshot is going to become a Standard Edition feature as well?

January 22, 2016 9:17 AM

RickHeiges said:

@ChrisP - Great Question.  This is my understanding.  As things are still being determined for what goes where in RTM, I have not heard any discussion about making DB Snapshots a standard edition feature.  However, you could have a Basic Availability Group in Enterprise Edition and therefore utilize a DB snapshot.

January 22, 2016 10:12 AM

Bert said:

I read it as meaning that if your version of SQL Server supports snapshots and you deploy a BAG, then you can take a snapshot of it.  You might still use BAGs with the enterprise edition, which is the only production edition that provides the snapshot feature.  

January 25, 2016 4:18 AM

RickHeiges said:

@Bert - That is the correct interpretation of it.

January 25, 2016 7:47 AM

Wes Brown said:

The problem is I have clients that still use DBM with certificates and without AD in place. That doesn't sound like it is going to be possible with 2016 BAG.

January 26, 2016 7:28 PM

Paul said:

Mirroring will probably be about for at least another version.  See: - it differentiates between two types of deprecated features.  Those not in next version.  And those not in future version.  Mirror falls under future which leads it being in the next version at least.

July 17, 2016 7:10 PM

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