Not all nodes have replicas. First of all, the number of replicas is determined by replication_factor which you set when creating the keyspace - and where they go is determined by replica_placement_strategy. Say, if you pick 3, the first copy of your item are placed based on token value of the node and other two replicas on nodes based on replica_placement_strategy. So when you add a node (thus its token) and decommission a node, it causes rebalance of the data thus streaming. Hope this helps.
-----Original Message----- From: buddhasystem [mailto:potek...@bnl.gov] Sent: Wednesday, January 26, 2011 5:14 PM To: cassandra-u...@incubator.apache.org Subject: Why does cassandra stream data when moving tokens? Sorry if this sounds silly, but I can't get my brain around this one: if all nodes contain replicas, why does the cluster stream data every time I more or remove a token? If the data is already there, what needs to be streamed? Thanks Maxim -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/Why-does-cassandra-stream-data-when-moving-tokens-tp5964839p5964839.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
