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I have recently learnt that the SQL server standard edition's basic availability group doesn't require a windows cluster.

Basic AG is considered equivalant to the deprecated mirroring technology. Like mirroring, the basic AG supports auto and manual failover.

However, mirroring supported auto failover only with the presense of witness server.

In availability groups there is no concept of witness server. So my question is - how is basic AG able to support automatic failover without the windows cluster? Or is the concept that - basic AG without cluster only supports manual failover, and basic AG with cluster supports automatic and manual failover?

I couldn't find documentation on this so any guidance will help me here.

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  • Hi, can you share where did you learn that AG may run without cluster? Commented Apr 21 at 20:01

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Just like any Availability Group, having the nodes in a cluster is required for automatic failover, and automatic failover between Failover Cluster instances is not allowed.

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  • FCI is not relevant to this question. Let's discuss purely about AGs. Thanks for your answer. May I ask - Is it correct to say that - for enterprise SQL AG if I only opt for manual failover then there is no need of cluster as well?
    – variable
    Commented Apr 21 at 21:43
  • Correct. For AGs the cluster only provides the quorum model and failure detection that enables automatic failover. Commented Apr 21 at 21:58

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