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Stale Cluster Notification

When information received by a peer node from the master node is more than 10 seconds old, the information is considered to be stale. A stale cluster does not guarantee that there is no change in the cluster. A stale cluster means that information held by the master node is not reaching a peer node. This can happen if the master node is not functioning correctly and does not send information to the peer node. A stale cluster can also occur if the master node does send information but it does not reach the peer node, due for example to a problem in the network. The notification sent for this scenario is shown in Table 6-17.

Table 6-17 The Cluster is in a Stale State

Transition (node A, node B) Notifications Sent 
(master, any) --> (stale cluster)CMM_STALE_CLUSTER(0)

Amnesia

Amnesia is an error condition in which a cluster restarts with stale cluster configuration data. This can happen when a cluster is restarted from a node that was not previously part of the most recent cluster membership list.

Split Brain

Split brain is an error condition in which there are two master nodes. This can be caused by interconnect failure between peer nodes.

During split brain, each master node assumes that it is the only master node in the cluster. A split brain can begin with any combination of roles for nodes A and B. The notification sent for this scenario is shown in Table 6-18.

Table 6-18 Two Masters in the Cluster (Split Brain)

Transition (node A, node B) Notifications Sent 
(any, any) --> (master, master )CMM_INVALID_CLUSTER

For information about how to recover from a split brain error condition, see theNetra High Availability Suite Foundation Services 2.1 6/03 Troubleshooting Guide.

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