Apache Cassandra™ 2.0

Virtual nodes

Overview of virtual nodes (vnodes).

Vnodes simplify many tasks in Cassandra:

  • You no longer have to calculate and assign tokens to each node.
  • Rebalancing a cluster is no longer necessary 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 and because data is sent to the replacement node incrementally instead of waiting until the end of the validation phase.
  • Improves the use of heterogeneous machines in a cluster. You can assign a proportional number of vnodes to smaller and larger machines.

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