Windows Server Failover Cluster Disk Witness Setup

Frequent Contributor

I have a Windows 2012 R2 failover cluster running a MSSQL 2014 cluster resource. It's a 2-node cluster with a disk [Q:] witness presented to the cluster from our SAN over fibre-channel. One thing I notice though is that this disk witness Q: is also a storage resource under the MSSQL cluster resource. Surely that's an incorrect configuration? My understanding is the disk witness should only be part of the core cluster resource and not assigned as storage to any sub resource?

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best response confirmed by shocko (Frequent Contributor)

Windows Server Failover Clustering (WSFC) is the features for providing high availability for SQL Server workloads - for both failover clustered instances and also Availablity Groups


Depending on the quorum configuration option that you choose and your specific settings, the cluster will be configured in one of the following quorum modes:


Node majority (no witness) - Only nodes have votes. No quorum witness is configured.
Node majority with witness (disk or file share) - Nodes have votes. In addition, a quorum witness has a vote. The cluster quorum is the majority of voting nodes in the active cluster membership plus a witness vote. A quorum witness can be a designated disk witness or a designated file share witness.
No majority (disk witness only) - No nodes have votes. Only a disk witness has a vote.
The cluster quorum is determined by the state of the disk witness.

Note: A Disk Witness isn't supported with Storage Spaces Direct.


  1. Disk witness
    Dedicated LUN that stores a copy of the cluster database
    Most useful for clusters with shared (not replicated) storage
  2. File share witness
    SMB file share that is configured on a file server running Windows Server
    Does not store a copy of the cluster database
  3. Cloud witness
    A witness file stored in Azure Blob Storage
    Recommended when all servers in the cluster have a reliable Internet connection.