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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 disk. There is no guarantee that the node with a functioning network
connection will gain control of the quorum disk. 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 network adapters 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 network
adapters that attach nodes to networks.
se500wbk1.book Page 58 Thursday, June 16, 2005 4:19 PM