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From "Hairong Kuang" <hair...@yahoo-inc.com>
Subject RE: Question on relocation of Hadoop cluster
Date Fri, 05 Oct 2007 16:32:02 GMT
Block locations are not persistent data. They are not kept any where after a
namenode shuts down. Instead each datanode reports its blocks to the
namenode at the startup time.

Hairong

-----Original Message-----
From: Taeho Kang [mailto:tkang1@gmail.com] 
Sent: Friday, October 05, 2007 12:51 AM
To: hadoop-user@lucene.apache.org
Subject: Re: Question on relocation of Hadoop cluster

Thanks again for your answer, Raghu.

Now, just out of my curiosity....

How are the exact locations of blocks/chunks being kept track of?
Is there any other mechanism/information that the namenode uses, other than
ip address or hostname, to manage the whereabouts of data blocks?


On 10/5/07, Raghu Angadi <rangadi@yahoo-inc.com> wrote:
>
>
> (I am not sure if I replied already...)
>
> Taeho Kang wrote:
> > Thanks for your quick reply, Raghu.
> >
> > The problem I am faced with is...
> > - I need to move my machines to a new location
>
> Assuming this goes well (i.e. no data loss),
>
> > - The new location will assign new ip addresses for my machines.
> > I am worried that this change of ip addresses may create havoc in 
> > the
> file
> > system ( i.e. discrepancy in file block info) once the cluster 
> > starts up
> in
> > the new location.
>
> this not an issue.
>
> > Is it going to be a problem?
>
> I don't think so.
>
> Raghu.
>



--
Taeho Kang [tkang.blogspot.com]
Software Engineer, NHN Corporation, Korea


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