Creating AG group on FCI

  • Hello,

    Can someone shed some lights on adding Availability Group with few databases to 2 Node Active\Active SQL Server Failover Cluster Instances (SS2019) in a single datacenter? They way I see that that could be configured, however the failover won't really work as a single node of a failover cluster cannot host more than one replica for the same availability group. Am I missing anything here?

    Thank you

     

  • It isn't clear what you are asking - or what problem you are trying to solve.

    Is it possible to add an AG to an FCI clustered instance?  Yes.

    Is it possible or advisable to set that AG secondary up for failover?  Maybe

    If all you have are 2 nodes in the cluster - then no, you cannot setup both an FCI and an AG and there really isn't any reason you would want to do that.

     

    Jeffrey Williams
    “We are all faced with a series of great opportunities brilliantly disguised as impossible situations.”

    ― Charles R. Swindoll

    How to post questions to get better answers faster
    Managing Transaction Logs

  • Thank you Jeffrey, sorry I wasn't clear.

    I was challenged by asking to fulfill the requirement to add an availability group to the existing 2 node FCI cluster.

    So from what I see, AG can be added to 2 node FCI cluster but failover wont work due to AG limitation.

    And the only way to fulfill that requirement is to add another node to 2 node FCI...

  • If the request isn't clear - then how could anyone provide a solution?  What is the goal of adding an AG to the FCI cluster - what is trying to be solved here?

    For example, if the goal is to create a DR instances - then a 3rd node in another data center as an AG is definitely a possibility and something to consider.  If the goal is to setup a read-only node for reporting/ETL/etc. processing then adding a 3rd node and creating an AG is a possible solution.

    If the request is to add an AG to the existing 2 nodes - then someone doesn't understand how a cluster works, nor do they understand how an FCI is configured vs an AG.

    I see a lot of people implementing AG's for the sake of implementing an AG because it is the 'newest' functionality and trying to avoid an FCI because somehow an AG is simpler?  It isn't necessarily any simpler - it has different requirements.

    Jeffrey Williams
    “We are all faced with a series of great opportunities brilliantly disguised as impossible situations.”

    ― Charles R. Swindoll

    How to post questions to get better answers faster
    Managing Transaction Logs

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