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From: Harsh J <harsh@cloudera.com>
Date: Mon, 17 Dec 2012 22:39:16 +0530
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 <CAOcnVr0MzbFMNeb-PQrj0fV3DtiBdWR7_WOaAmvN9XsDWZAUuw@mail.gmail.com>
Subject: Re: Is it necessary to run secondary namenode when starting HDFS?
To: "<user@hadoop.apache.org>" <user@hadoop.apache.org>
Content-Type: text/plain; charset=ISO-8859-1

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