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From Bill Au <bill.w...@gmail.com>
Subject Re: Downgrading Hdfs
Date Wed, 18 Mar 2009 18:35:39 GMT
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.


   3. stop all applications and make sure that there are no running tasks.
   4. stop HDFS cluster.


   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.



On Wed, Mar 18, 2009 at 1:08 PM, David Ritch <david.ritch@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

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