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MapReduce >> mail # user >> NameNode failure and recovery!


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Re: NameNode failure and recovery!
If you are not in position to go for HA just keep your checkpoint period
shorter to have recent data recoverable from SNN.

and you always have a option
hadoop namenode -recover
try this on testing cluster and get versed to it.

and take backup of image at some solid state storage.


Shashwat Shriparv

On Wed, Apr 3, 2013 at 9:56 PM, Harsh J <[EMAIL PROTECTED]> wrote:

> There is a 3rd, most excellent way: Use HDFS's own HA, see
>
> http://hadoop.apache.org/docs/current/hadoop-yarn/hadoop-yarn-site/HDFSHighAvailabilityWithQJM.html
> :)
>
> On Wed, Apr 3, 2013 at 8:10 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
> >
> >
>
>
>
> --
> Harsh J
>
NEW: Monitor These Apps!
elasticsearch, apache solr, apache hbase, hadoop, redis, casssandra, amazon cloudwatch, mysql, memcached, apache kafka, apache zookeeper, apache storm, ubuntu, centOS, red hat, debian, puppet labs, java, senseiDB