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From "Ozcan ILIKHAN" <ilik...@cs.wisc.edu>
Subject Re: Backup NameNode
Date Fri, 08 Oct 2010 06:30:56 GMT
How should configuration files of Active and Backup NameNode should differ from each other?

Assume that our Active NameNode died, do we need to anything further DNS record change? We
start our Backup NameNode with "-backup" argument.  How to convert role to active?

From: Dhruba Borthakur 
Sent: Friday, October 08, 2010 12:49 AM
To: hdfs-user@hadoop.apache.org 
Subject: Re: Backup NameNode

ActiveNameNode and BackupNamenode do not automatically  exchange roles ever.  DataNodes are
not informed. One can use Virtual IP failover  or DNS to switch so that DataNodes need not
know that the Namenode has moved from one machine to another. 

hope this helps,

On Wed, Oct 6, 2010 at 10:07 PM, Ozcan ILIKHAN <ilikhan@cs.wisc.edu> wrote:

  Hi all,

  Following questions are specific to v0.21.0.

  From the user guide it is not clear enough how Active NameNode and Backup Namenode take
over role from each other, how DateNode are informed if active NameNode  fails (or do they
need to be informed?). What is happening in disaster scnerios.

  While configuring cluster, assume 1 active NameNode, 1 Backup NameNode, 1 Chekpoint NameNode,
and the rest of the cluster is assumed to be DataNodes.  Which parameters for these 4 types
of nodes' hdfs-site.xml and core-site.xml  should set, and how should they (config files of
4 type of nodes ) differ from each other.

  By the way, in order to understand certain functionalities, most of the time we need to
go deep into source code. I think it will be good to enrich Hadoop (especially HDFS) documentation.

  Thanks in advance,

Connect to me at http://www.facebook.com/dhruba

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