Users Guide

Cluster quorum

A witness disk is used when there is a node or network communication failure where the nodes 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 remain as part of the cluster to maintain quorum. Use witness

disks on clusters with even number of storage nodes to ensure there is a vote majority in case of a split-

brain situation.

There are two options for witness disks — disk witness and file share witness. Dell recommends you to

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.

There are different types of quorum modes:

• Node majority

– Recommended for SOFS clusters with an odd number of storage 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 SOFS clusters with an even number of storage 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 Dell PowerEdge R730 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 Dell PowerEdge R630 storage nodes. Setting 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"