StackOverflow2013

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PO
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20004595
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2013-11-15T15:31:04.660
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2013-11-15T18:01:02.163
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2013-11-15T18:01:02.163
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text
Body
4) Partition ranges are determined by granting each node the range from their available tokens up until the next specified token. 2)Data is exchanged through gossip detailing which nodes have which tokens. This meta-data allows every node to know which nodes are responsible for which ranges. Keyspace/Replication settings also change where data is actually saved. EXAMPLE: 1)A gets 256 ranges B gets 256 Ranges. But to make this simple lets give them each 2 tokens and pretend the token range is 0 to 30 Given tokens: A 10,15 and B 3,11 Nodes are responsible for the following ranges <pre><code>(3-9:B)(10:A)(11-14:B)(15-30,0-2:A) </code></pre> 3)If C Joins also with 2 tokens 20,5 Nodes will now be responsible for the following ranges <pre><code>(3-4:B)(5-9:C)(10:A)(11-14:B)(15-19:A)(20-30,0-2:C) </code></pre> Vnodes are powerful because now when C joins the cluster it gets its data from multiple nodes (5-9 from B and 20-30,0-2 from A) sharing the load between those machines. In this toy example you can see that having only 2 tokens allows for some nodes to host the majority of the data while others get almost none. As the number of Vnodes increases the balance between the nodes increases as the ranges become randomly subdivided more and more. At 256 nodes you are extremely likely to have distributed an even amount of data to each node in the cluster. For more information VNodes: <a href="http://www.datastax.com/dev/blog/virtual-nodes-in-cassandra-1-2">http://www.datastax.com/dev/blog/virtual-nodes-in-cassandra-1-2</a>
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1. This table or related slice is empty.
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1. POCassandra num_tokens - is this really num_token_partitions?
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1. PTAnswer
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1. USRussS
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1. USRussS
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1. POCassandra num_tokens - is this really num_token_partitions?
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1. COReally nice answer. Thanks so much!
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