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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "HadoopSupport" by jeremyhanna
Date Mon, 19 May 2014 13:25:59 GMT
Dear Wiki user,

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

The "HadoopSupport" page has been changed by jeremyhanna:
https://wiki.apache.org/cassandra/HadoopSupport?action=diff&rev1=59&rev2=60

Comment:
noting new consistency level default

  }}}
  The settings normally default to 4 each, but some find that too conservative.  If you set
it too low, you might have blacklisted tasktrackers and failed jobs because of occasional
timeout exceptions.  If you set them too high, jobs that would otherwise fail quickly take
a long time to fail, sacrificing efficiency.  Keep in mind that this can just cover a problem.
 It may be that you always want these settings to be higher when operating against Cassandra.
 However, if you run into these exceptions too frequently, there may be a problem with your
Cassandra or Hadoop configuration.
  
+ If you are seeing inconsistent data coming back, consider the consistency level at which
you read ('''cassandra.consistencylevel.read''') and write ('''cassandra.consistencylevel.write''').
 Both properties default to !ConsistencyLevel.LOCAL_ONE (Previously [[https://issues.apache.org/jira/browse/CASSANDRA-6214|ONE]]).
- If you are seeing inconsistent data coming back, consider the consistency level that you
are reading and writing at.  The two relevant properties are:
- 
-  * '''cassandra.consistencylevel.read''' - defaults to !ConsistencyLevel.ONE.
-  * '''cassandra.consistencylevel.write''' - defaults to !ConsistencyLevel.ONE.
  
  Also hadoop integration uses range scans underneath which do not do read repair.  However
reading at !ConsistencyLevel.QUORUM will reconcile differences among nodes read.  See ReadRepair
section as well as the !ConsistencyLevel section of the [[http://wiki.apache.org/cassandra/API|API]]
page for more details.
  

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