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From Apache Wiki <>
Subject [Cassandra Wiki] Update of "VirtualNodes/Balance" by EricEvans
Date Thu, 02 Aug 2012 18:19:03 GMT
Dear Wiki user,

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The "VirtualNodes/Balance" page has been changed by EricEvans:

shuffles as long running tasks

   * "Shuffling node at a time means that for each node i for i in 0..N-1 (where N is the
cluster size), i/N of the ranges shuffled will, on average, have been shuffled at least once
already. So it's substantially less efficient than shuffling once, then assigning the vnodes
out in one cluster-wide pass." -- ''Jonathan Ellis''<<FootNote([[|CASSANDRA-4443#comment-13423505]])>>
+  * Shuffling will entail moving a ''lot'' of data around the cluster and so has the potential
to consume a lot of disk and network I/O, and to take a considerable amount of time.  For
this to be an online operation, the shuffle will need to operate on a lower priority basis
to other streaming operations, and should be expected to take days or weeks to complete.
  === Nodes / Cluster ===
  The most straightforward method of effecting ownership is a token move (i.e. relocating
a range from one node to another).  Exposing this with JMX would allow implementing all of
the required operations client-side.

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