As long as the version upgrade has not been finalized, here's the procedure I use to downgrade:
1. make sure that the previous version upgrade has not been finalized. A version upgrade cannot be rollback if it has been finalized. bin/hadoop dfsadmin -upgradeProgress status 2. stop map-reduce cluster. bin/stop-mapred.sh 3. stop all applications and make sure that there are no running tasks. 4. stop HDFS cluster. bin/stop-dfs.sh 5. rollback version of Hadoop. Install previous version of Hadoop if previous version of Hadoop has been removed from the system. 6. start HDFS with the rollback option. bin/start-dfs.sh -rollback 7. monitor the rollback until it is complete. bin/hadoop dfsadmin -upgradeProgress status 8. start map-reduce cluster. bin/start-mapred.sh Bill On Wed, Mar 18, 2009 at 1:08 PM, David Ritch <david.ri...@gmail.com> wrote: > There is an established procedure for upgrading from one release of Hadoop > to a newer release. Is there something similar to move back to an > lower-numered release? > > Specifically, we have data in a cloud running Hadoop-19.0. Because of > stability issues, we are wondering whether we should move back to 18, but > we > don't want to lose our data. Is there a downward migration path? > > Thanks, > > David >
