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From "Chanchal James" <chanc...@gmail.com>
Subject Re: Question about Hadoop
Date Thu, 12 Jun 2008 17:15:30 GMT
Thanks Lohit for the info. I have one more question.
If I keep all data in HDFS, is there anyway I can back it up regularly.
While testing I had to delete the temporary "datastore" folder and reformat
the file system a couple of times. So while using Hadoop in a real
environment, what are the chances of such software side uncorrectable
problems to occur. Can we correct it without a reformat ? I cannot afford to
loose the data I plan to put in HDFS.

Thank you.

On Thu, Jun 12, 2008 at 12:02 PM, lohit <lohit_bv@yahoo.com> wrote:

> Ideally what you would want is your data to be on HDFS and run your
> map/reduce jobs on that data. Hadoop framework splits you data and feeds in
> those splits to each map or reduce task. One problem with Image files is
> that you will not be able to split them. Alternatively people have done
> this, they wrap Image files within xml and create huge files which has
> multiple image files in them. Hadoop offers something called streaming using
> which you will be able to split the files at xml boundry and feed it to your
> map/reduce tasks. Streaming also enables you to use any code like
> perl/php/c++.
> Check info about streaming here
> http://hadoop.apache.org/core/docs/r0.17.0/streaming.html
> And information about parsing XML files in streaming in here
> http://hadoop.apache.org/core/docs/r0.17.0/streaming.html#How+do+I+parse+XML+documents+using+streaming%3F
>
> Thanks,
> Lohit
>
> ----- Original Message ----
> From: Chanchal James <chanch13@gmail.com>
> To: core-user@hadoop.apache.org
> Sent: Thursday, June 12, 2008 9:42:46 AM
> Subject: Question about Hadoop
>
> Hi,
>
>
>
> I have a question about Hadoop. I am a beginner and just testing Hadoop.
>
> Would like to know how a php application would benefit from this, say an
>
> application that needs to work on a large number of image files. Do I have
> to
>
> store the application in HDFS always, or do I just copy it to HDFS when
>
> needed, do the processing, and then copy it back to the local file system ?
>
> Is that the case with the data files too ? Once I have Hadoop running, do I
>
> keep all data & application files in HDFS always, and not use local file
>
> system storage ?
>
>
>
> Thank you.
>
>

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