Home | About | Sematext search-lucene.com search-hadoop.com
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
 Search Hadoop and all its subprojects:

Switch to Threaded View
MapReduce >> mail # user >> NameNode failure and recovery!


Copy link to this message
-
NameNode failure and recovery!
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
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