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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Thu, 02 Aug 2012 18:19:03 -0000
Message-ID: <20120802181903.31808.86345@eos.apache.org>
Subject: 
 =?utf-8?q?=5BCassandra_Wiki=5D_Update_of_=22VirtualNodes/Balance=22_by_Er?=
 =?utf-8?q?icEvans?=
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The "VirtualNodes/Balance" page has been changed by EricEvans:
http://wiki.apache.org/cassandra/VirtualNodes/Balance?action=3Ddiff&rev1=3D=
5&rev2=3D6

Comment:
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 effici=
ent than shuffling once, then assigning the vnodes out in one cluster-wide =
pass." -- ''Jonathan Ellis''<<FootNote([[https://issues.apache.org/jira/bro=
wse/CASSANDRA-4443?focusedCommentId=3D13423505&page=3Dcom.atlassian.jira.pl=
ugin.system.issuetabpanels:comment-tabpanel#comment-13423505|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 shu=
ffle will need to operate on a lower priority basis to other streaming oper=
ations, and should be expected to take days or weeks to complete.
+ =

  =3D=3D=3D Nodes / Cluster =3D=3D=3D
  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 w=
ould allow implementing all of the required operations client-side.
 =20