Rebalancing a cluster
Cluster rebalancing ensures that each node in a Cassandra cluster manages an equal amount of data. Rebalancing a cluster is a DataStax Enterprise feature only.
Cluster rebalancing ensures that each node in a Cassandra cluster manages an equal amount of data. Rebalancing a cluster is an enterprise-only feature. Currently, OpsCenter only supports rebalancing on clusters using the random partitioner or murmur 3 partitioner. Ordered partitioners are not supported. A rebalance is usually required only when the cluster topology has changed in some way, such as nodes were added or removed, or the replica placement strategy was changed.
A cluster is considered balanced when each node is responsible for an equal range of data. OpsCenter determines cluster balance by evaluating the partitioner tokens assigned to each node to make sure that the data ranges each node is responsible for are evenly distributed. Even though a cluster is considered balanced, it is still possible that some nodes have more data relative to others because only the number of rows (not the size of rows) managed by each node is taken into account.
The optimal path to rebalance clusters with around 100 nodes or less is determined by calculating the number of moves required and how much streaming data those moves would entail. If a cluster contains more than around 100 nodes, the optimal path is calculated based on simply the number of moves to expedite the rebalancing process.