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Measures reported by ClusterNwTest
A network (sometimes called an interconnect) performs one of the following roles in a cluster:
- A private network carries internal cluster communication. The Cluster service authenticates all internal communication, but administrators who are particularly concerned about security can restrict internal communication to physically secure networks.
- A public network provides client systems with access to cluster application services. IP Address resources are created on networks that provide clients with access to cluster services.
- A mixed (public-and-private) network carries internal cluster communication and connects client systems to cluster application services.
- A network that is not enabled for use by the cluster (that is, neither public nor private) carries traffic unrelated to cluster operation.
Regardless of the role that a network performs, its availability is critical to the smooth functioning of the cluster, as without the network, communication between cluster nodes and between clients and cluster nodes become impossible.
The ClusterNetworks test indicates whether the cluster networks are up or down.
| Measurement |
Description |
Measurement
Unit |
Interpretation |
| Network_up |
Indicates the number of cluster networks that are currently available. |
Number |
|
| Network_down |
Indicates the number of cluster networks that are currently unavailable. |
Number |
If there is only one cluster network available in a cluster and it goes down, the cluster nodes stop communicating with each other. When two nodes are unable to communicate, they are said to be partitioned. After two nodes become partitioned, the Cluster service automatically shuts down on one node to guarantee the consistency of application data and the cluster configuration. This can lead to the unavailability of all cluster resources.
Therefore, it is recommended that you configure multiple networks as private or mixed to protect the cluster from a single network failure. For instance, if each node has at least two networks configured, and both are say, mixed networks, the Cluster service can tolerate network failures. In this scenario, the Cluster service can detect a public network adapter failure and fail over all resources that depend on that adapter (through its IP address) to a node where this network is available. This is accomplished because the private network is still functioning properly. If, on the other hand, an adapter on the private network fails, the Cluster service can use the public network for internal communication. This is accomplished because the public network is mixed, allowing both internal and client traffic.
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