Hi Jerry,
efer to the following links for reference:

1. the hadoop version used in the doc may be different from yours, but they
are good references to understand the basic flow.
2. suggest create a test cluster that could mimic your production
environment, try it out on the test cluster before on the production.
3. backup your namenode meta data, which may help you to recover.
4. the official rollback functionality does not work in hadoop 1.0.1 so be
prepared if the upgrade failed.
On Thu, Mar 6, 2014 at 12:47 PM, Jerry Zhang <[EMAIL PROTECTED]> wrote:

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