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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.

   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.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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