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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "Operations" by JonathanEllis
Date Wed, 09 Dec 2009 16:19:23 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for change notification.

The "Operations" page has been changed by JonathanEllis.
http://wiki.apache.org/cassandra/Operations?action=diff&rev1=8&rev2=9

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   * !RackAwareStrategy: replica 2 is is placed in the first node along the ring the belongs
in '''another''' data center than the first; the remaining N-2 replicas, if any, are placed
on the first nodes along the ring in the '''same''' rack as the first
  
  Note that with !RackAwareStrategy, succeeding nodes along the ring should alternate data
centers to avoid hot spots.  For instance, if you have nodes A, B, C, and D in increasing
Token order, and instead of alternating you place A and B in DC1, and C and D in DC2, then
nodes C and A will have disproportionately more data on them because they will be the replica
destination for every Token range in the other data center.
+  * The corollary to this is, if you want to start with a single DC and add another later,
when you add the second DC you should add as many nodes as you have in the first rather than
adding a node or two at a time gradually.
  
  Replication strategy may not be changed without wiping your data and starting over.
  

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