Cluster definitions, Node, Cluster Resource and Group, Cluster Heartbeat, Quorum, Cluster-aware and Cluster-unaware application, Failover and Failback

What is a Node?

A node is an independent server that is a member of a cluster.

What is a a Cluster Resource?

A cluster resource is a network application or service defined and managed by the cluster application. Click the following link to know more about cluster resource and cluster resource group.

What is Cluster Resource Group?

Cluster resources are hold together in a cluster within a cluster resource group, or a cluster group. Cluster groups are the units of failover within the cluster. When a cluster resource fails and cannot be restarted automatically, the entire cluster group is taken offline and failed over to another available cluster node. Click the following link to know more about cluster resource and cluster resource group.

What is Cluster Heartbeat?

The Cluster service transmits heartbeat messages on a dedicated network adapter to other server nodes in the server cluster. The cluster heartbeat is used to track the condition of each node in the cluster. If the Cluster service doesn’t receive a heartbeat from a server in the cluster within a specified time, the service assumes the server has failed and initiates failover.

What is Cluster Quorum?

A quorum is the shared storage facility that keeps the cluster resource database and logs. In a typical MSCS cluster, the Quorum is located on a shared storage device.

What is Local Quorum?

Local quorum also contains the cluster configuration data but it is kept on a node's local disk. The local quorum resource is useful for single-node cluster configurations (used only for testing and development).

What is Majority Node Set (MNS) resource?

The Majority Node Set (MNS) resource is the quorum resource used for a Majority Node Set cluster.

What is Cluster-aware Application?

A cluster-aware application is developed in such a way that the Cluster Service can test the application availability to determine whether it is functioning as desired. When a cluster-aware application fails, the cluster can stop and restart the application as necessary on the same node or in another node.

What is Cluster-unaware application?

A cluster-unaware application is not programmed to work on a cluster.

What is Failover?

Failover is the process of a cluster group moving from the current active node to another available node in the cluster, in case of a failure. Click the following link to learn more about the Failover and Failback.

What is Failback?

Failback Failback is the process of a cluster group moving back to a node after a hardware restore. Click the following link to learn more about the Failover and Failback.