How to Set Up a Majority Node Set (Server Clusters: Majority Node Set Quorum)

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP2

The majority node set resource is an optional quorum resource that we ship with the MSCS. By default, the physical disk resource is setup as a quorum resource.

Setting up a MNS cluster is no different to setting up a standard cluster. The only difference will be the location of the quorum and the fact that the user can choose not to nominate a disk located on a shared storage interconnect as a quorum disk.

If there is a shared storage, set up can be done using standard mechanisms. The quorum disk can be located on the shared interconnect or as a local quorum disk. Once installation is complete, open Cluster Administrator and create a new MNS resource in the cluster group. Bring it online. Then go to the cluster properties and change the cluster quorum to the newly created MNS resource.

If there is no shared interconnect, the cluster configuration wizard will create a single-node local quorum disk cluster by default. The procedure for creating an MNS quorum resource and using it is the same as above.

Once a single node cluster is set up, the quorum resource can be switched to the majority node set resource using cluster administrator as follows:

• Open cluster administrator and connect to the appropriate cluster.

• Create a new resource of type Majority node set.

• Change the cluster quorum resource to the newly created majority node set resource. The Quorum tab on the cluster properties sheet shows the current quorum resource and it can be modified by selecting the appropriate resource.

Once a single node cluster is set up using the majority node set resource, other nodes can be added to the cluster. As each node is joined, the quorum calculation is updated. In other words, if two nodes are added to build a three-node cluster, quorum is adjusted so that two out of the three nodes must be running for the cluster to be considered as having quorum.

The majority node set quorum resource ensures that the quorum data is kept consistent across all nodes of the cluster and it is responsible for making changes to the quorum data stored on all nodes in the cluster.

Each node in the cluster stores its quorum data in the following directory on the system disk:

%SystemRoot%\Cluster\MNS.%ResourceGUID%$\%ResourceGUID%$\MSCS

The contents of this directory should not be modified; this directory contains cluster configuration information. Modifying the data in this directory may mean that the cluster service cannot start on the node.

The quorum resource accesses the data on the other nodes in the cluster using a network share. When a node is added to a cluster using the majority node set resource, a file share is created to expose the cluster quorum data to the majority node set resource. The share name is defined as follows:

\\%NodeName%\%ResourceGUID%$

The share is created with local system access. Since the cluster service is running under a domain account that is also a member of the local system group, the majority node set resource has access to the share.

To avoid potential security issues and issues where the cluster service cannot access the share, the permissions or security attributes associated with this file share should not be modified. It is recommended that default setting be used and no changes be made to ACLs governing the share created to be used by the Cluster service.

Since we use SMB shares as a MNS quorum device the cluster service now have to rely on an "external" component to provide a critical infrastructure for cluster service to be functional. SMB has two components, LanManServer and LanManWorkstation, which install as separate services in Server 2003. Both these services need to be running otherwise the cluster nodes will not be able to publish shares or communicate with the shares on other cluster nodes.