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HDFS, mail # user - NameNode fails


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Re: NameNode fails
Mohammad Tariq 2012-07-20, 11:39
Hi Yogesh,

      Follow the link specified by Bejoy. It shows all the necessary steps.

Regards,
    Mohammad Tariq
On Fri, Jul 20, 2012 at 4:14 PM, Bejoy Ks <[EMAIL PROTECTED]> wrote:
> Hi Yogesh
>
> Just treat SecondaryName Node as a check pointing node. Name recovery
> is mostly done by writing the fsimage and edit log to a remote nfs
> mount other than the local fs. So that if the copy on local disk gets
> corrupted or lost on a disk failure or machine failure the one from
> remote mount can be used.
>
> You can read more here
> http://wiki.apache.org/hadoop/NameNodeFailover
>
> Regards
> Bejoy KS
>
>
> On Fri, Jul 20, 2012 at 3:58 PM,  <[EMAIL PROTECTED]> wrote:
>> Thanks Mohammad :-),
>>
>> I just read this concept of secondary NameNode. Thank you for your reply.
>> Mohammad I am not finding the way to implement would you please explain me regarding to recover namenode, Iam getting confuse.
>>
>> Thanks & Regards
>> Yogesh Kumar Dhari
>>
>> ________________________________________
>> From: Mohammad Tariq [[EMAIL PROTECTED]]
>> Sent: Friday, July 20, 2012 3:17 PM
>> To: [EMAIL PROTECTED]
>> Subject: Re: NameNode fails
>>
>> Hi yogesh,
>>
>>        First of all, we should always keep it mind that Secondary
>> Namenode is not a backup for the Namenode. By its name, it gives a
>> sense that its a backup for the Namenode, but in reality its not.
>> Namenode stores data in 2 files :
>> 1- fsimage - snapshot of the filesystem when namenode started
>> 2- Edit logs - contain the sequence of changes made to the filesystem
>> after namenode started.
>>
>> The sole purpose of Secondary Namenode is to have a checkpoint in HDFS
>> and it acts as a helper of the Namenode. It basically :
>> 1- gets the edit logs from the namenode in regular intervals and
>> applies to fsimage
>> 2- once it has new fsimage, it copies back to namenode
>>
>> Namenode uses this fsimage for the next restart.
>>
>> Regards,
>>     Mohammad Tariq
>>
>>
>> On Fri, Jul 20, 2012 at 1:59 PM,  <[EMAIL PROTECTED]> wrote:
>>> Hi Bejoy,
>>>
>>> Its done now, Error log was showing namenode is not formated,
>>> I closed all previous terminal and restarted it after formatting.
>>>
>>> its running now.
>>>
>>> Please suggest me that if in case it gets crashed then how do I recover it
>>> from Secondary Namenode. how should I proceed for that
>>>
>>>
>>> Thanks & regards
>>> Yogesh Kumar Dhari
>>> ________________________________
>>> From: Bejoy KS [[EMAIL PROTECTED]]
>>> Sent: Friday, July 20, 2012 12:56 PM
>>> To: Yogesh Kumar (WT01 - Communication and Media);
>>> [EMAIL PROTECTED]
>>> Subject: Re: NameNode fails
>>>
>>> Hi Yogesh
>>>
>>> Please post in the error logs/messages if you find any.
>>>
>>> Regards
>>> Bejoy KS
>>>
>>> Sent from handheld, please excuse typos.
>>> ________________________________
>>> From: <[EMAIL PROTECTED]>
>>> Date: Fri, 20 Jul 2012 07:21:24 +0000
>>> To: <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
>>> Subject: RE: NameNode fails
>>>
>>> Thanks Bejoy, Mohammad and Vignesh :-).
>>>
>>> I have done the suggested by you and made thses changes. and formatted the
>>> namenode and trying to start cluster.
>>> but now name node is not starting :-(
>>>
>>>
>>> hdfs-site.xml
>>>
>>> **********************************************************
>>> <configuration>
>>>     <property>
>>>         <name>dfs.replication</name>
>>>         <value>1</value>
>>>     </property>
>>>
>>>     <property>
>>>         <name>dfs.name.dir</name>
>>>         <value>/HADOOP/hadoop-0.20.2/hadoop_name_dirr</value>
>>>     </property>
>>>
>>>     <property>
>>>         <name>dfs.data.dir</name>
>>>         <value>/HADOOP/hadoop-0.20.2/hadoop_data_dirr</value>
>>>     </property>
>>>
>>> </configuration>
>>>
>>> **************************************************************
>>>
>>>
>>>
>>> hdfs-core.xml
>>>
>>> **************************************************************
>>>
>>> <configuration>
>>>     <property>