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From Harsh J <ha...@cloudera.com>
Subject Re: Is it necessary to run secondary namenode when starting HDFS?
Date Mon, 17 Dec 2012 17:09:16 GMT
The SecondaryNameNode is necessary for automatic maintenance in
long-running clusters (read: production), but is not necessary for,
nor tied into the basic functions/operations of HDFS.

On 1.x, you can remove the script's startup of SNN by removing its
host entry from the conf/masters file.
On 2.x, you can selectively start the NN and DNs by using the
hadoop-daemon.sh script commands.

On Mon, Dec 17, 2012 at 10:34 PM, Ivan Ryndin <iryndin@gmail.com> 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,

Harsh J

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