Product Documentation

Synchronization Across Cluster Nodes

Aug 31, 2016

All configurations on a NetScaler cluster are performed on the cluster IP address, which is the management address of the cluster. This cluster IP address is owned by a cluster node that is referred to as the cluster configuration coordinator as shown in the following figure:



The configurations that are available on the configuration coordinator are automatically propagated to the other cluster nodes and therefore all cluster nodes have the same configurations.

Note:
  • NetScaler allows only a few configurations to be performed on individual cluster nodes through their NetScaler IP (NSIP) address. These configurations are not propagated across the other cluster nodes. For more information, see "Operations Supported on Individual Cluster Nodes".
  • The following commands when executed on the cluster IP address are not propagated to other cluster nodes:
    • shutdown: Shuts down only the configuration coordinator.
    • reboot: Reboots only the configuration coordinator.
    • rm cluster instance: Removes the cluster instance from the node that you are executing the command on.
  • If the NetScaler cluster is configured to use a quorum (quorum is mandatory for versions prior to NetScaler 10.5), a command is propagated to the other cluster nodes only when a majority of the nodes are in synch. If a majority of the nodes are not in synch or are in the process of synchronizing, the new commands cannot be accepted and therefore command propagation is temporarily halted.

When a node is added to a cluster, the configurations and the files (SSL certificates, licenses, DNS, and so on) that are available on the cluster configuration coordinator are synchronized to the newly added cluster node. When an existing cluster node, that was intentionally disabled or that had failed, is once again added, the cluster compares the configurations available on the node with the configurations available on the configuration coordinator. If there is a mismatch in configurations, the node is synchronized by using one of the following:

  • Full synchronization. If the difference between configurations exceeds 255 commands, all the configurations of the configuration coordinator are applied to the node that is rejoining the cluster. The node remains operationally unavailable for the duration of the synchronization.
  • Incremental Synchronization. If the difference between configurations is less than or equal to 255 commands, only the configurations that are not available are applied to the node that is rejoining the cluster. The operational state of the node remains unaffected.
Note: You can also manually synchronize the configurations and files. For more information, see "Synchronizing Cluster Configurations" and "Synchronizing Cluster Files".