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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Trivial Update of "NameNode" by SteveLoughran
Date Wed, 24 Jun 2009 10:19:21 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 SteveLoughran:
http://wiki.apache.org/hadoop/NameNode

The comment on the change is:
new page

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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.  HDFS is not currently a
High Availability system. When the NameNode goes down, the file system goes offline.  There
is an optional SecondaryNameNode that can be hosted on a separate machine.  It only creates
checkpoints of the namespace by merging the edits file into the fsimage file and does not
provide any real redundancy.
+ The NameNode is a [Single Point of Failure] for the HDFS Cluster.  HDFS is not currently
a High Availability system. When the NameNode goes down, the file system goes offline.  There
is an optional SecondaryNameNode that can be hosted on a separate machine.  It only creates
checkpoints of the namespace by merging 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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