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The "Operations" page has been changed by JonathanEllis. The comment on this change is: change NTS recommendation to alternate DCs. http://wiki.apache.org/cassandra/Operations?action=diff&rev1=90&rev2=91 -------------------------------------------------- === Token selection === Using a strong hash function means !RandomPartitioner keys will, on average, be evenly spread across the Token space, but you can still have imbalances if your Tokens do not divide up the range evenly, so you should specify !InitialToken to your first nodes as `i * (2**127 / N)` for i = 0 .. N-1. In Cassandra 0.7, you should specify `initial_token` in `cassandra.yaml`. - With !NetworkTopologyStrategy, you should calculate the tokens the nodes in each DC independantly. Tokens still neded to be unique, so you can add 1 to the tokens in the 2nd DC, add 2 in the 3rd, and so on. Thus, for a 4-node cluster in 2 datacenters, you would have + With !NetworkTopologyStrategy, you should alternate data centers when assigning tokens. For example, with two nodes in each of two data centers, + {{{ - DC1 - node 1 = 0 + [DC1] node 1 = 0 + [DC2] node 2 = 42535295865117307932921825928971026432 - node 2 = 85070591730234615865843651857942052864 + [DC1] node 3 = 85070591730234615865843651857942052864 + [DC2] node 4 = 127605887595351923798765477786913079296 - - DC2 - node 1 = 1 - node 2 = 85070591730234615865843651857942052865 }}} - With order preserving partitioners, your key distribution will be application-dependent. You should still take your best guess at specifying initial tokens (guided by sampling actual data, if possible), but you will be more dependent on active load balancing (see below) and/or adding new nodes to hot spots. Once data is placed on the cluster, the partitioner may not be changed without wiping and starting over.
