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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "NameNode" by AllenWittenauer
Date Sat, 06 Sep 2008 14:55:47 GMT
Dear Wiki user,

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

The following page has been changed by AllenWittenauer:
http://wiki.apache.org/hadoop/NameNode

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  Client applications talk to the NameNode whenever they wish to locate a file, or when they
want to add/copy/move/delete a file. The NameNode responds the successful requests by returning
a list of relevant DataNode servers where the data lives.
  
- The NameNode is a Single Point of Failure for the HDFS Cluster. There is support for NameNodeFailover,
with a SecondaryNameNode hosted on a separate machine being able to stand in for the original
NameNode if it goes down. However, HDFS is not currently a HighAvailability filesystem. When
the NameNode goes down, the filesystem goes offline.
+ The NameNode is a Single Point of Failure for the HDFS Cluster.  HDFS is not currently a
HighAvailability filesystem. When the NameNode goes down, the filesystem goes offline.  There
is an optional SecondaryNameNode that can be hosted on a separate machine.  It only merges
the edits file into the fsimage file and does not provide any real redundancy.
  
  It is essential to look after the NameNode. Here are some recommendations from production
use
  

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