Hello all, I wanted to share my experience with you who wanted to upgrade Hadoop from 0.12 or previous versions to more recent versions like 0.16
After installing 0.16 and tried start-dfs.sh, Namenode gave me an exception saying I had to use "-upgrade" option. I gave "-upgrade" option and Namenode and Datanodes came up alright. But when I tried finalizing the upgrade, but it didn't work, nor did "-rollback" option work. >From there on, the only way I could have the cluster up and running was to give "-upgrade" option. So here is my advice : Move to 0.13 first and then do the upgrade from there. However, following the steps found in the wiki, I was able to upgrade from 0.12 to 0.13 alright. I hope it's not going to be too painful upgrading from 0.13 to 0.14 or upwards, using "-upgrade / -rollback / -finalize" options :-) Also, if anybody wanted to share any good or painful experience with me, I would really appreciate it! /Taeho