Virtual nodes

Overview of virtual nodes (vnodes).

Virtual nodes, known as Vnodes, distribute data across nodes at a finer granularity than can be easily achieved if calculated tokens are used. Vnodes simplify many tasks in Cassandra:

Tokens are automatically calculated and assigned to each node.
Rebalancing a cluster is automatically accomplished when adding or removing nodes. When a node joins the cluster, it assumes responsibility for an even portion of data from the other nodes in the cluster. If a node fails, the load is spread evenly across other nodes in the cluster.
Rebuilding a dead node is faster because it involves every other node in the cluster.
The proportion of vnodes assigned to each machine in a cluster can be assigned, so smaller and larger computers can be used in building a cluster.

For more information, see the article Virtual nodes in Cassandra 1.2. To convert an existing cluster to vnodes, see Enabling virtual nodes on an existing production cluster.

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