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MapReduce, mail # user - Is it necessary to run secondary namenode when starting HDFS?

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Re: Is it necessary to run secondary namenode when starting HDFS?
Ivan Ryndin 2012-12-17, 17:23
Thank you very much, Bryan!

It is now clear for me, that in development mode I'll not start secondary
But in production it's better to have it.

2012/12/17 Bryan Beaudreault <[EMAIL PROTECTED]>

> You don't need a secondary name node.  It creates snapshots of the name
> node metadata periodically, which helps to keep down the size of the edits
> files.  If you don't run one, over time your edits files will grow.  The
> next time you go to restart your namenode, it could take a very long time
> to start up if your edits are large.  I recommend running one in
> production, to reduce the amount of downtime if you need to replace or
> restart your namenode.  If that isn't a concern for you then you don't need
> it.
> On Mon, Dec 17, 2012 at 12:04 PM, Ivan Ryndin <[EMAIL PROTECTED]> wrote:
>> Hi all,
>> is it necessary to run secondary namenode when starting HDFS?
>> I am dealing with Hadoop 1.1.1.
>> Looking at script $HADOOP_HOME/bin/start_dfs.sh
>> There are next lines in this file:
>> # start dfs daemons
>> # start namenode after datanodes, to minimize time namenode is up w/o data
>> # note: datanodes will log connection errors until namenode starts
>> "$bin"/hadoop-daemon.sh --config $HADOOP_CONF_DIR start namenode
>> $nameStartOpt
>> "$bin"/hadoop-daemons.sh --config $HADOOP_CONF_DIR start datanode
>> $dataStartOpt
>> "$bin"/hadoop-daemons.sh --config $HADOOP_CONF_DIR --hosts masters start
>> secondarynamenode
>>  So, will HDFS work if I turn off starting of secondarynamenode ?
>> I do ask this because I am playing with Hadoop on two-node cluster only
>> (and machines in cluster do not have much RAM and disk space), and thus
>> don't want to run unnecessary processes.
>> --
>> Best regards,
>> Ivan P. Ryndin,
Best regards,
Ivan P. Ryndin