Dell PowerVault 775N (Rackmount NAS Appliance) - Manual (Page 74)

Preventing Network Failure
The Cluster Service uses all available private and public-and-private networks for internal communication. Configure multiple
networks as private or public-and-private to protect the cluster from a single network failure. If there is only one such
network available and it fails, the cluster nodes stop communicating with each other. When two nodes are unable to
communicate, they are partitioned and the Cluster Service automatically shuts down on one node. While this shutdown
guarantees the consistency of application data and the cluster configuration, it can make cluster resources unavailable.
For example, if each node has only one network adapter, and the network cable on one of the nodes fails, each node,
(because it is unable to communicate with the other), attempts to take control of the quorum resource. There is no guarantee
that the node with a functioning network connection will gain control of the quorum resource. If the node with the failed
network cable gains control, the entire cluster is unavailable to network clients. To avoid this problem, ensure that all nodes
have at least two networks and are configured to use both networks for the private network (internal communications).
Node-to-Node Communication
The Cluster Service does not use public only networks for internal communication. For example, a cluster has Network A
configured as private and Network B configured as public. If Network A fails, the Cluster Service does not use Network B
because it is public; the nodes stop communicating and one node terminates its Cluster Service.
Network Interfaces
The Microsoft Windows® operating system keeps track of all NICs in a server cluster. This tracking system allows you to view
the state of all cluster network interfaces from a cluster management application, such as Cluster Administrator.
Cluster Nodes
A cluster node is a system in a server cluster that has a working installation of the
Windows operating system and the Cluster Service.
Cluster nodes have the following characteristics:
Every node is attached to one or more cluster storage devices. Each cluster storage device attaches to one or more
disks. The disks store all of the cluster's configuration and resource data. Each disk can be owned by only one node at
any point in time, but ownership can be transferred between nodes. The result is that each node has access to all
cluster configuration data.
Every node communicates with the other nodes in the cluster through one or more NICs that attach nodes to networks.
Every node in the cluster is aware of another system joining or leaving the cluster.
Every node in the cluster is aware of the resources that are running on all nodes in the cluster.
All nodes in the cluster are grouped under a common cluster name, which is used when accessing and managing the
cluster.
Table 7-1 defines various states of a node that can occur in cluster operation.