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MapReduce >> mail # user >> Uploading a file to HDFS


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Karim Awara 2013-09-26, 10:11
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Shekhar Sharma 2013-09-26, 10:45
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Jitendra Yadav 2013-09-26, 11:25
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Karim Awara 2013-09-26, 12:51
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Re: Uploading a file to HDFS
Karim!

Look at DFSOutputStream.java:DataStreamer

HTH
Ravi
________________________________
 From: Karim Awara <[EMAIL PROTECTED]>
To: user <[EMAIL PROTECTED]>
Sent: Thursday, September 26, 2013 7:51 AM
Subject: Re: Uploading a file to HDFS
 

Thanks for the reply. when the client caches 64KB of data on its own side, do you know which set of major java classes/files responsible for such action?
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Best Regards,
Karim Ahmed Awara
On Thu, Sep 26, 2013 at 2:25 PM, Jitendra Yadav <[EMAIL PROTECTED]> wrote:

Case 2:
>
>
>
>While selecting target DN in case of write operations, NN
will always prefers first DN as same DN from where client  sending the
data, in some cases NN ignore that DN when there is some disk space issues or
some other health symptoms found,rest of things will same.
>
>
>Thanks
>Jitendra
>
>
>
>On Thu, Sep 26, 2013 at 4:15 PM, Shekhar Sharma <[EMAIL PROTECTED]> wrote:
>
>Its not the namenode that does the reading or breaking of the file..
>>When you run the command hadoop fs -put <input> <output>.....
>>Here "hadoop" is a script file which is default client for hadoop..and
>>when the client contacts the namenode for writing, then NN creates a
>>block id and ask 3 dN to host the block ( replication factor to 3) and
>>this information is sent to client.
>>
>>client caches 64KB of data on its own side and then pushes the data to
>>the DN and then this data gets pushed through pipeline..and this
>>process gets repeated till 64MB data is written and if the client
>>wants to to write more then he will again contact NN via heart beat
>>signal and this process continuess...
>>
>>Check how does writing happens in HDFS?
>>
>>
>>Regards,
>>Som Shekhar Sharma
>>+91-8197243810
>>
>>
>>
>>On Thu, Sep 26, 2013 at 3:41 PM, Karim Awara <[EMAIL PROTECTED]> wrote:
>>> Hi,
>>>
>>> I have a couple of questions about the process of uploading a large file (>
>>> 10GB) to HDFS.
>>>
>>> To make sure my understanding is correct, assuming I have a cluster of N
>>> machines.
>>>
>>> What happens in the following:
>>>
>>>
>>> Case 1:
>>>                 assuming i want to uppload a file (input.txt) of size K GBs
>>> that resides on the local disk of machine 1 (which happens to be the
>>> namenode only). if I am running the command  -put input.txt {some hdfs dir}
>>> from the namenode (assuming it does not play the datanode role), then will
>>> the namenode read the first 64MB in a temporary pipe and then transfers it
>>> to one of the cluster datanodes once finished?  Or the namenode does not do
>>> any reading of the file, but rather asks a certain datanode to read the 64MB
>>> window from the file remotely?
>>>
>>>
>>> Case 2:
>>>              assume machine 1 is the namenode, but i run the -put command
>>> from machine 3 (which is a datanode). who will start reading the file?
>>>
>>>
>>>
>>> --
>>> Best Regards,
>>> Karim Ahmed Awara
>>>
>>> ________________________________
>>> This message and its contents, including attachments are intended solely for
>>> the original recipient. If you are not the intended recipient or have
>>> received this message in error, please notify me immediately and delete this
>>> message from your computer system. Any unauthorized use or distribution is
>>> prohibited. Please consider the environment before printing this email.
>>
>

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This message and its contents, including attachments are intended solely for the original recipient. If you are not the intended recipient or have received this message in error, please notify me immediately and delete this message from your computer system. Any unauthorized use or distribution is prohibited. Please consider the environment before printing this email.
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Jay Vyas 2013-10-01, 21:29