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
