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Hadoop, mail # user - Re: Hadoop noob question


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Rahul Bhattacharjee 2013-05-11, 15:41
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Nitin Pawar 2013-05-11, 15:50
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Mohammad Tariq 2013-05-11, 16:03
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Nitin Pawar 2013-05-11, 16:05
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Shahab Yunus 2013-05-11, 16:10
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Mohammad Tariq 2013-05-11, 17:04
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Re: Hadoop noob question
Rahul Bhattacharjee 2013-05-11, 17:16
Thanks Tariq!
On Sat, May 11, 2013 at 10:34 PM, Mohammad Tariq <[EMAIL PROTECTED]> wrote:

> @Rahul : Yes. distcp can do that.
>
> And, bigger the files lesser the metadata hence lesser memory consumption.
>
> Warm Regards,
> Tariq
> cloudfront.blogspot.com
>
>
> On Sat, May 11, 2013 at 9:40 PM, Rahul Bhattacharjee <
> [EMAIL PROTECTED]> wrote:
>
>> IMHO,I think the statement about NN with regard to block metadata is more
>> like a general statement. Even if you put lots of small files of combined
>> size 10 TB , you need to have a capable NN.
>>
>> can disct cp be used to copy local - to - hdfs ?
>>
>> Thanks,
>> Rahul
>>
>>
>> On Sat, May 11, 2013 at 9:35 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:
>>
>>> absolutely rite Mohammad
>>>
>>>
>>> On Sat, May 11, 2013 at 9:33 PM, Mohammad Tariq <[EMAIL PROTECTED]>wrote:
>>>
>>>> Sorry for barging in guys. I think Nitin is talking about this :
>>>>
>>>> Every file and block in HDFS is treated as an object and for each
>>>> object around 200B of metadata get created. So the NN should be powerful
>>>> enough to handle that much metadata, since it is going to be in-memory.
>>>> Actually memory is the most important metric when it comes to NN.
>>>>
>>>> Am I correct @Nitin?
>>>>
>>>> @Thoihen : As Nitin has said, when you talk about that much data you
>>>> don't actually just do a "put". You could use something like "distcp" for
>>>> parallel copying. A better approach would be to use a data aggregation tool
>>>> like Flume or Chukwa, as Nitin has already pointed. Facebook uses their own
>>>> data aggregation tool, called Scribe for this purpose.
>>>>
>>>> Warm Regards,
>>>> Tariq
>>>> cloudfront.blogspot.com
>>>>
>>>>
>>>> On Sat, May 11, 2013 at 9:20 PM, Nitin Pawar <[EMAIL PROTECTED]>wrote:
>>>>
>>>>> NN would still be in picture because it will be writing a lot of meta
>>>>> data for each individual file. so you will need a NN capable enough which
>>>>> can store the metadata for your entire dataset. Data will never go to NN
>>>>> but lot of metadata about data will be on NN so its always good idea to
>>>>> have a strong NN.
>>>>>
>>>>>
>>>>> On Sat, May 11, 2013 at 9:11 PM, Rahul Bhattacharjee <
>>>>> [EMAIL PROTECTED]> wrote:
>>>>>
>>>>>> @Nitin , parallel dfs to write to hdfs is great , but could not
>>>>>> understand the meaning of capable NN. As I know , the NN would not be a
>>>>>> part of the actual data write pipeline , means that the data would not
>>>>>> travel through the NN , the dfs would contact the NN from time to time to
>>>>>> get locations of DN as where to store the data blocks.
>>>>>>
>>>>>> Thanks,
>>>>>> Rahul
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Sat, May 11, 2013 at 4:54 PM, Nitin Pawar <[EMAIL PROTECTED]
>>>>>> > wrote:
>>>>>>
>>>>>>> is it safe? .. there is no direct answer yes or no
>>>>>>>
>>>>>>> when you say , you have files worth 10TB files and you want to
>>>>>>> upload  to HDFS, several factors come into picture
>>>>>>>
>>>>>>> 1) Is the machine in the same network as your hadoop cluster?
>>>>>>> 2) If there guarantee that network will not go down?
>>>>>>>
>>>>>>> and Most importantly I assume that you have a capable hadoop
>>>>>>> cluster. By that I mean you have a capable namenode.
>>>>>>>
>>>>>>> I would definitely not write files sequentially in HDFS. I would
>>>>>>> prefer to write files in parallel to hdfs to utilize the DFS write features
>>>>>>> to speed up the process.
>>>>>>> you can hdfs put command in parallel manner and in my experience it
>>>>>>> has not failed when we write a lot of data.
>>>>>>>
>>>>>>>
>>>>>>> On Sat, May 11, 2013 at 4:38 PM, maisnam ns <[EMAIL PROTECTED]>wrote:
>>>>>>>
>>>>>>>> @Nitin Pawar , thanks for clearing my doubts .
>>>>>>>>
>>>>>>>> But I have one more question , say I have 10 TB data in the
>>>>>>>> pipeline .
>>>>>>>>
>>>>>>>> Is it perfectly OK to use hadopo fs put command to upload these
>>>>>>>> files of size 10 TB and is there any limit to the file size  using hadoop
>>>>>
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Mohammad Tariq 2013-05-11, 17:22
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Rahul Bhattacharjee 2013-05-12, 12:30
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Mohammad Tariq 2013-05-12, 12:10