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Does a node that reboots to regain quorum get removed from dynamic quorum? RRS feed

  • Question

  • In the cluster logs I've seen some pretty crazy connection matrix's. When this happens cluster will have some of the nodes restart their cluster services in hopes that it will clear the issue up. If dynamic quorum is enabled will a node that restarts cluster service for this purpose get removed from the dynamic quorum count?

    In the situations where I've run into this I've wanted the nodes vote to be counted; some node could talk to it. But Dynamic Quorum adds a random variable into the mix. If I have good (from my point of view) nodes that are restarting cluster service, and a WAN failure happens, quorum might be formed when I didn't want it to, because dynamic quorum removed those nodes from the count.

    Friday, October 11, 2013 10:49 PM

Answers

  • I don't believe I need further assistance. It sounds like WFC doesn't special case dynamic vote count due to intentional reboots to fix up the connectivity matrix. In my mind that makes dynamic quorum possibly too risky because it leaves itself vulnerable to networking grey failures.
    Friday, October 18, 2013 2:47 PM

All replies

  • You don't state the OS version, but since you are asking about dynamic quorum, I will assume 2012 R2.

    The witness disk/share is added/removed as nodes are added removed.  Each node is always given vote, unless you do something that would remove it, but by default, each node will always have a vote.  The witness disk/share is what is given a quorum vote or denied a quorum vote, depending upon the number of nodes in the cluster.  Only the witness disk/share needs to be changed because there will always be either an odd or even number of nodes in the cluster.


    .:|:.:|:. tim

    Monday, October 14, 2013 10:29 PM
  • I'm asking about Windows 2012, the version where Dynamic Quorum was introduced. I'm not talking about Dynamic Witness. 
    Tuesday, October 15, 2013 4:43 AM
  • From TechNet's description - "When this option [dynamic quorum] is enabled, the cluster dynamically manages the vote assignment to nodes, based on the state of each node. Votes are automatically removed from nodes that leave active cluster membership, and a vote is automatically assigned when a node rejoins the cluster. "

    So, when they are part of the cluster, they will get their vote, unless you have disabled it for that node.  When cluster service is not running, it does not hold active cluster membership.  When cluster service is running and has joined the server to the cluster, it is an active member.


    .:|:.:|:. tim

    Wednesday, October 16, 2013 1:30 AM
  • Dynamic quorum will kick in only when the vote count is about to go under 50%. Once there the dynamic quorum will turn off vote for the node with lowest nodeID.

    Now if you have two of the lowest nodeID machines bouncing, there will be a change of 0 & 1 that you will see.


    yup

    Thursday, October 17, 2013 2:00 PM
  • I don't believe I need further assistance. It sounds like WFC doesn't special case dynamic vote count due to intentional reboots to fix up the connectivity matrix. In my mind that makes dynamic quorum possibly too risky because it leaves itself vulnerable to networking grey failures.
    Friday, October 18, 2013 2:47 PM