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?
--
Best Regards,
Karim Ahmed Awara
On Thu, Sep 26, 2013 at 2:25 PM, Jitendra Yadav
<jeetuyadav200...@gmail.com>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 <shekhar2...@gmail.com>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 <karim.aw...@kaust.edu.sa>
>> 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
>> >
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>
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