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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Trivial Update of "Operations" by jeremyhanna
Date Wed, 05 May 2010 22:26:47 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 jeremyhanna.
The comment on this change is: Fixed a couple of typos.
http://wiki.apache.org/cassandra/Operations?action=diff&rev1=42&rev2=43

--------------------------------------------------

  === 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 = 1 .. N.
  
- With order preserving partioners, 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.
+ 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.
  
@@ -30, +30 @@

  A Cassandra cluster always divides up the key space into ranges delimited by Tokens as described
above, but additional replica placement is customizable via !IReplicaPlacementStrategy in
the configuration file.  The standard strategies are
  
   * !RackUnawareStrategy: replicas are always placed on the next (in increasing Token order)
N-1 nodes along the ring
-  * !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
+  * !RackAwareStrategy: replica 2 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.
  

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