Although Hadoop is designed and developed for distributed computing it= can be run on a single node in pseudo distributed mode and with multiple d= ata node on single machine . Developers often run multiple data nodes on si= ngle node to develop and test distributed features,data node behavior, Name node interaction with data node and for = other reasons.

Please go through following blog for same..

http://w= ww.blogger.com/blogger.g?blogID=3D2277703965936900657#editor/target=3Dpost;= postID=3D8231904039775612388

Fro= m: Robert Evans [evans@yahoo-inc.com]
Sent: Tuesday, March 05, 2013 11:57 PM
To: user= @hadoop.apache.org
Subject: Re: Hadoop cluster setup - could not see second datanode

Why would you need several data nodes? It is simple to have one = data node and one name node on the same machine. I believe that you c= an make multiple data nodes run on the same machine, but it would take quit= e a bit of configuration work to do it, and it would only really be helpful for you to do some very specific testing i= nvolving multiple data nodes.

--Bobby

From: =C2=F4=B1=A8=B5=C4=D0=A1=D0= =D0=BC=D2 <85469843= @qq.com>
Reply-To: "user@hadoop.apache.org" &= lt;user@hadoop.= apache.org>
Date: Tuesday, March 5, 2013 8:41 A= M
To: user <user@hadoop.apache.org>
Subject: Re:RE: Hadoop cluster setu= p - could not see second datanode

Hello,

Can Namenode and several datanodes exist in one machine?

I only have one PC. I want to configure it like this way.

BRs//Julian

----= -------------- Original ------------------

From: "AMARNATH, Balachandar"<BALACHANDAR.AMARNATH= @airbus.com>;

Date: Tue, Mar 5, 2013 07:55 PM

To: "user@hadoop.apache.org"<user@hadoop.apache.org>;

Subject: RE: Hadoop cluster setup - could not see second = datanode

I fixed it the below issue J

Regards

Bala

From: AMA= RNATH, Balachandar [mailto:BALACHANDAR.AMARNATH@airbus.com]
Sent: 05 March 2013 17:05
To: user= @hadoop.apache.org
Subject: Hadoop cluster setup - could not see second datanode=

Thanks for the info= rmation,

Now I am trying to = install hadoop dfs using 2 nodes. A namenode cum datanode, and a separate d= ata node. I use the following configuration for my hdfs-site.xml

<configuration&g= t;

<property= >

<n= ame>fs.default.name= </name>

<v= alue>localhost:9000</value>

</propert= y>

<property= >

<n= ame>dfs.data.dir</name>

<v= alue>/home/bala/data</value>

</propert= y>

<property= >

<n= ame>dfs.name.dir</name>

<v= alue>/home/bala/name</value>

</propert= y>

</configuration&= gt;

In namenode, I have= added the datanode hostnames (machine1 and machine2).

When I do ‘st= art-all.sh’, I see the log that the data node is starting in both the= machines but I went to the browser in the namenode, I see only one live node. (That is the namenode which is configured as dat= anode)

Any hint here will = help me

With regards=

Bala

From: Mah= esh Balija [mailto:balijamahesh.mca@gmail.com]
Sent: 05 March 2013 14:15
To: user= @hadoop.apache.org
Subject: Re: Hadoop file system

You can be able to use Hdfs alone in the distributed mode to fulfill your r= equirement.
Hdfs has the Filesystem java api through which you can interact with the HD= FS from your client.
HDFS is good if you have less number of files with huge size rather than yo= u having many files with small size.

Best,
Mahesh Balija,
Calsoft Labs.

On Tue, Mar 5, 2013 at 10= :43 AM, AMARNATH, Balachandar <BALACHANDAR.AMARNATH@airbus.com> wrote:<= /p>

Hi,

I am new to hdfs. In my java application, I need to per= form ‘similar operation’ over large number of files. I would li= ke to store those files in distributed machines. I don’t think, I will need map reduce paradigm. But however I would = like to use HDFS for file storage and access. Is it possible (or nice idea)= to use HDFS as a stand alone stuff? And, java APIs are available to work w= ith HDFS so that I can read/write in distributed environment ? Any thoughts here will be helpful.

With thanks and regards

Balachandar

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