CHAPTER 4 Displaying clusters

Performance Manager displays clusters using the new auto-discovery feature. There are some differences in PM’s operation for TruCluster Production Server (TruCluster Version 3.5) and TruCluster Server (TruCluster Version 5.0). With TruCluster Server, PM recognizes cluster aliases and does not use director names.

Auto-discovery for Clusters

When you add a node, Performance Manager checks to see if it belongs to a cluster or is a cluster alias. PM does this by querying the node for a cluster name or director name. If a value for either cluster name or director name is returned, the cluster populates the GUI with its members. If the returned value is for cluster name, PM recognizes the cluster as a TruCluster Server and populates the GUI using the cluster name (the default cluster alias) and displaying all of its members. If the returned value is for director name, PM recognizes the cluster as a TruCluster Production Server, and creates a cluster entity using the director name for the cluster. The cluster entity queries the node’s membership table and populates the GUI with the members.

Display Representation of Clusters

When monitoring a cluster, Performance Manager discovers all the members of the cluster. When the membership changes, Performance Manager adjusts its representation of the cluster as follows:

If a node was added to the cluster, a new icon for that node is added. If the cluster has any active displays, the display adjusts to include the new node.
If a node was removed from the cluster, Performance Manager deletes the icon for that node from its view of the cluster. Any active displays for the cluster adjust to remove the deleted node.
If the deleted node has any displays defined explicitly for that node, they are deleted from the session. If the deleted node subsequently returns to the session, Performance Manager adds it to the cluster view. However, node-specific displays will not be recreated. Currently, the only way to regain these node-specific displays is manually redefining them or reloading them from a saved session.

Possible Anomalies for TruCluster Production Server

Director name changes may result in two cluster nodes for the same cluster appearing in Performance Manager. This may happen if attempts to get cluster information from a node occur during the change and s node is removed from the cluster as described above, If the nodes(s) removed from the cluster notices the new director names before the cluster node notices it, the removed node will create a new cluster node with the new name.

Usually the pre-existing cluster node notices the director name change, and also notices there is already a cluster node with the same name. In that case it does the following:

Moves its displays and thresholds to the new node.
Removes its children, allowing the new cluster to acquire them.
Deletes itself from the session.

If the pre-existing node removes all of its children because it could not get information from them, it will continue asking for information from the last node that it polled. If this node never responds, this cluster node will continue to exist without children even if a new cluster node has been created based on information from the other nodes.

To avoid conflicts between group names and cluster node (director) names, do not give group nodes the same names as cluster director names. This interferes with cluster auto-discovery.

For example, if you give the same name as a cluster director when a corresponding cluster node does not exist in the session, and then add nodes from that cluster to the session, the cluster nodes will not be created.