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I have a Always On AG 2016, configured on Windows Server 2012 R2 – 2 node cluster. Quorum configured as 2 nodes + Fileshare witness, totally 3 votes.

Scenario 1: Now, either 1 node fails – remaining vote = 66.66 (majority) and cluster is up.

Scenario 2: Now, fileshare witness fails – remaining = 66.66 (majority) and cluster is up

Kindly help me understand the dynamic quorum and dynamic witness on scenario 2.

My doubts, post scenario 2:

Will it automatically take away 1 vote from either one of the nodes? If yes, remaining vote will be 33% not majority and single point of failure.

What will be the role of dynamic witness in this scenario?

Thanks in advance!.

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  • In scenario 2 you have 2 nodes up and running and only FS witness failed correct ?
    – Shanky
    May 20, 2019 at 7:12
  • @Shanky: Yes, correct. May 20, 2019 at 7:14

1 Answer 1

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Will it automatically take away 1 vote from either one of the nodes? If yes, remaining vote will be 33% not majority and single point of failure.

Yes correct. Dynamic witness works in such a way that it tires to keep total number of votes odd. In your case when the FS witness is down the Dynamic quorum will toggle one vote from one of the node such that its vote becomes zero and total votes now voting would be one.

The dynamic quorum and witness are very much interrelated. In above case the process of adapting quorum after FS witness failed is actually dynamic quorum. It adjusted itself after the failure.

I would strongly suggest you to read Understanding cluster and pool quorum

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  • The link you have given is specifically for azure stack storage clusters. I cannot find a similar concept of dynamic quorum and dynamic witness for onpremise wsfc. Can you update the link if you find it?
    – variable
    May 12, 2022 at 7:19
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    @variable Instead of questioning every time if you would spend time in reading you would have read and seen that at the very starting the article says Applies to: Azure Stack HCI, versions 21H2 and 20H2; Windows Server 2022, Windows Server 2019 :). It applies to WSFC no matter on Azure or On-premise.
    – Shanky
    May 12, 2022 at 7:36
  • Ok I got confused since this article learn.microsoft.com/en-us/windows-server/failover-clustering/… mentions under point 3 that - Allow cluster to dynamically manage the assignment of node votes This option is not present in Windows Server 2016 and above.
    – variable
    May 12, 2022 at 7:43

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