Upgrading an existing cluster to vnodes

The text discusses the process of upgrading an existing single token per node architecture to vnodes without any downtime in a Cassandra cluster. It explains that enabling vnodes involves setting the num_tokens parameter and restarting the node, which splits the current range into the specified number of tokens while maintaining contiguousness. To realize the benefits of vnodes, the 'cassandra-shuffle' utility is used to randomly redistribute the vnodes amongst the cluster. The upgrade procedure can be tested on a per-datacenter basis and may require adjustments in workflow, such as using nodetool status instead of nodetool ring and removehost instead of removetoken for node removal. Despite some variance in the 'owns' percentage, this is normal and expected with vnodes.