A Shared Disk Witness Has Been Detected

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at http://go.microsoft.com/fwlink/?linkid=34707.]  

Topic Last Modified: 2008-03-19

The Microsoft Exchange Analyzer Tool examines the following registry entry to determine the version of the Microsoft Windows operating system that is running on the computer:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\CurrentVersion

Version values are as follows:


CurrentVersion value Microsoft Windows operating system


Microsoft Windows NT® Server 4.0


Microsoft Windows 2000 Server


Microsoft Windows Server™ 2003


Microsoft Windows Server 2008

Next, the Exchange Analyzer queries the Active Directory directory service to determine the value of the msExchClusterStorageType attribute of the Mailbox server objects.

A value of 1 for the msExchClusterStorageType attribute indicates that the clustered mailbox server is hosted in a Cluster continuous replication (CCR) environment, and a value of 2 indicates that the clustered mailbox server is in a Single copy cluster (SCC). A value of <Not Set> indicates that the Mailbox server is a stand-alone server.

The Exchange Server Analyzer then queries the QuorumType property of the MSCluster_Cluster Microsoft Windows® Management Instrumentation (WMI) class to determine whether the quorum type set is Node Majority.

The Node Majority quorum type can sustain failures of half the nodes minus 1.

Finally, the Exchange Server Analyzer queries the MSCluster_Resource (WMI) class to determine whether a quorum resource has been defined as a shared disk witness.

The quorum resource allows the cluster to maintain its state and configuration independently of individual node failures. The quorum resource stores a constantly-updated version of the cluster database and is accessible to all cluster nodes.

Failover clusters with an even number of nodes usually use a quorum resource configuration that includes a "witness disk" or "witness file share." In a cluster with an even number of nodes and a quorum configuration that includes a witness, when the witness remains online, the cluster can sustain failures of half the nodes.

If the Exchange Server Analyzer determines that all of the following conditions exist, the Exchange Server Analyzer displays a warning:

  • The computer is running on the Windows Server 2008 operating system as a node in a cluster.

  • The quorum type is set to Node Majority.

  • The cluster type is Cluster continuous replication (CCR).

  • The quorum resource is a 'shared witness disk'.

A Windows Server 2008 CCR Node Majority Quorum with a shared witness disk as the quorum resource is not a recommended configuration.

If a shared storage (witness disk) quorum is used for CCR, the entire system must be listed in the Microsoft Windows Server Catalog of Tested Products.

To address this error, it is recommended that a File Share Witness be configured as the Cluster Witness quorum resource. You should setup and secure a file share on a separate computer, then configure the cluster to use a Node and File Share Majority quorum.

On Windows Server 2008, if a Node and File Share Majority quorum type is used for CCR, the nodes do not have to be listed in the Microsoft Windows Server Catalog of Tested Products.

To setup a file share as the quorum resource
  1. Follow the guidance of the Exchange 2007 topic How to Configure the Node and File Share Majority Quorum (http://go.microsoft.com/fwlink/?LinkId=114002)

For more information about Exchange 2007 CCR on Windows Server 2008, see Installing Cluster Continuous Replication on Windows Server 2008 (http://go.microsoft.com/fwlink/?LinkId=103636)