title: Cassandra cleanup on several servers at once
body: <p>We have a big Cassandra cluster 18 Servers (on one server near 5T data )</p>
  
  <p><a href="http://docs.datastax.com/en/cassandra/2.0/cassandra/operations/ops_add_node_to_cluster_t.html" rel="nofollow noreferrer">http://docs.datastax.com/en/cassandra/2.0/cassandra/operations/ops_add_node_to_cluster_t.html</a> - We have added a new nodes following this documentation .</p>
  
  <p>After we have added new servers, we began the process of cleaning data (nodetool cleanup)</p>
  
  <p>In the documentation advise: After all new nodes are running, run nodetool cleanup on each of the previously existing nodes to remove the keys no longer belonging to those nodes. Wait for cleanup to complete on one node before doing the next)</p>
  
  <p>But cleanup for one server takes near 2 - 3 days in our case. 
  My question is can I start cleaning at once on multiple servers, 2 or 3 ... </p>
  
  <p>Or it may lead to data loss ?</p>
  
  <p>Some more info .</p>
  
  <p>We use cassandra 2.0.13 with vnodes . Also We keep files in blons in cassandra .</p>
  
  <p>Replication factor = 3 </p>