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From Apache Wiki <wikidi...@apache.org>
Subject [Lucene-hadoop Wiki] Update of "NameNodeFailover" by TedDunning
Date Fri, 20 Jul 2007 18:15:56 GMT
Dear Wiki user,

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The following page has been changed by TedDunning:
http://wiki.apache.org/lucene-hadoop/NameNodeFailover

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  That said, there is a secondary name node that talks to the primary name node on a regular
basis in order to keep track of the files in the system.  It does this by copying the fsimage
and editlog files from the primary name node.
  
- If the name node dies, the best procedure is to simply use DNS to rename the primary and
secondary name nodes.  The secondary name node will serve as primary name node as long as
nodes request meta-data from it.  Once you get your old primary back up, you should reconfigure
it to be the secondary name node and you will be back in full operation.
+ If the name node dies, the simplest procedure is to simply use DNS to rename the primary
and secondary name nodes.  The secondary name node will serve as primary name node as long
as nodes request meta-data from it.  Once you get your old primary back up, you should reconfigure
it to be the secondary name node and you will be back in full operation.
+ 
+ Note that the secondary name node only copies information every few minutes.  For a more
up-to-date recovery, you can make the name node log transactions to multiple directories,
including one networked mounted one.  You can then copy the fsimage and fsedit files from
that networked directory and have a recovery that is up to the second.
  
  Questions I still have include:
  
- * what do you have to do to the old primary to make it be a secondary?
+  * what do you have to do to the old primary to make it be a secondary?
  
- * can you have more than one secondary name node (for off-site backup purposes)?
+  * can you have more than one secondary name node (for off-site backup purposes)?
  
- * are there plans for distributing the name node function?  
+  * are there plans for distributing the name node function?  
  

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