Cluster patching terms and concepts

The following table describes some key cluster patching terminology and concepts.

Table 1. Cluster patching key terms and concepts
Term	Description
Cluster	One or more servers working together, which appear to the end user as one entity to provide a platform to run applications and services. The system of clustering provides a backup and reserve capability for the applications running on the cluster.
Node	One server or unit member of a cluster. A cluster is made up of a number of nodes.
Group	A container for resources. Resources that have a link or dependency on each other must be in the same group.
Resource	The lowest entity managed by a cluster. Some resources can have a dependency on others and require other resources to be online before they come online. This is sometimes built in as some resources are integral to a cluster being formed and maintaining functionality. These resources are created and grouped by the Windows® cluster management application.
Quorum	The quorum is a set of files used by the cluster to maintain the cluster. The quorum is integral to a cluster functioning. The quorum contains the configuration files used by the cluster to ensure the cluster is maintained in an operational state.
Quorum configuration	Describes how the quorum is set up in the cluster. Each cluster has one quorum configuration. For more information, see the following resources: Windows 2003 systems: http://technet.microsoft.com/en-us/library/cc779076(v=ws.10).aspx Windows 2008 systems: http://technet.microsoft.com/en-us/library/cc731739.aspx Windows 2012 systems: http://technet.microsoft.com/en-us/library/jj612870.aspx#BKMK_option_overview
Failover	The process of groups being moved from one node to another node in the event of a failure of the node the resource is currently running on.
Node up or active	When a node is active, the node can receive and run groups from another node and participate fully in all clustering functions and is available to receive groups in the event of a failure of another node in the cluster.
Pause or paused node	Pause node brings the node into a paused state. While a node is paused the clustering service is still running on the node, however, the node no longer accepts any new groups onto the node and therefore is not available in a failover situation. The node continues to run any groups on the node before it was paused.
Resume node	Resuming a node restarts the clustering service on the node and changes the node from a paused or down state to an up state.
Node down	If a node is down it is no longer running the cluster service and is not available for any clustering activity. It is not available to run any applications or services for the cluster. Any groups running on the node before it goes down are failed over onto a different node.
Move group	A move group command moves groups from the node the command is run against to another available node in the cluster. Other nodes must be available for this command to work successful.