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Dell Storage with Microsoft Storage Spaces Best Practices Guide

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Cluster quorum

A witness disk is used when there is a node or network communication failure where the node continue to operate but can no longer communicate between one another. The witness disk acts as part of the voting process to determine which nodes remains as part of the cluster to maintain quorum. Use witness disks on clusters with even number of storage or compute nodes to ensure that there is a vote majority in case of a split-brain situation.

There are two options for cluster quorum witness, a disk witness and file share witness. For SOFS configurations, Dell recommends that you use file share witness because a continuously available SMB share can be created on the SOFS cluster to host the witness disk. You can create the file-share witness disk on a small 3 GB, two-way mirror VD without storage tiers.

For Converged configurations, Dell recommends that the quorum disk be located on its own CSV within any storage pool that is accessible to all nodes.

There are different types of quorum modes:
  • Node majority
    • Recommended for clusters with an odd number of cluster nodes (for example, 3x3)
    • All nodes that are online and can communicate, have a vote and the cluster is operational when votes are over 50 percent.
  • Node and disk majority
    • Each node and the witness disk, which is part of cluster, has a vote.

  • Node and file share majority

    • Recommended for clusters with an even number of cluster nodes (for example, 4x4).
    • Each node and the file share witness has a vote.

Run the following PowerShell command to create the cluster quorum disk. 

Set-ClusterQuorum <Mode> <PathToResource>

For example, a 3x3 configuration with three DSMS 730 Storage nodes. Setting quorum mode to node majority with no file share or disk witness on cluster named MYCLUSTER. 

Set-ClusterQuorum –NodeMajority –Cluster MYCLUSTER

For example, a 4x4 configuration with four DSMS 630 storage nodes. Set quorum mode to node and file share majority with a 1 GB VD setup as a SOFS file share. The cluster is named MYCLUSTER and file share is named FileShareWitness. 

Set-ClusterQuorum -NodeAndFileShareMajority "\\MYCLUSTER\FileShareWitness"

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