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HDFS, mail # user - Re: NameNode failure and recovery!


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Re: NameNode failure and recovery!
Mohammad Tariq 2013-04-03, 16:16
If it's not possible to restart the NN daemon on the same box, then yes.

Warm Regards,
Tariq
https://mtariq.jux.com/
cloudfront.blogspot.com
On Wed, Apr 3, 2013 at 9:30 PM, Rahul Bhattacharjee <[EMAIL PROTECTED]
> wrote:

> Thanks to all of you for precise and complete responses.
>
> S
> o in case of failure we have to bring another backup system up with the
> fsimage and edit logs from the NFS filer.
> SNN stays as is for the new NN.
>
> Thanks,
> Rahul
>
>
> On Wed, Apr 3, 2013 at 8:38 PM, Azuryy Yu <[EMAIL PROTECTED]> wrote:
>
>> for Hadoopv2, there is HA, so SNN is not necessary.
>> On Apr 3, 2013 10:41 PM, "Rahul Bhattacharjee" <[EMAIL PROTECTED]>
>> wrote:
>>
>>> Hi all,
>>>
>>> I was reading about Hadoop and got to know that there are two ways to
>>> protect against the name node failures.
>>>
>>> 1) To write to a nfs mount along with the usual local disk.
>>>  -or-
>>> 2) Use secondary name node. In case of failure of NN , the SNN can take
>>> in charge.
>>>
>>> My questions :-
>>>
>>> 1) SNN is always lagging , so when SNN becomes primary in event of a NN
>>> failure ,  then the edits which have not been merged into the image file
>>> would be lost , so the system of SNN would not be consistent with the NN
>>> before its failure.
>>>
>>> 2) Also I have read that other purpose of SNN is to periodically merge
>>> the edit logs with the image file. In case a setup goes with option #1
>>> (writing to NFS, no SNN) , then who does this merging.
>>>
>>> Thanks,
>>> Rahul
>>>
>>>
>>>
>