[ http://issues.apache.org/jira/browse/HADOOP-702?page=all ]

Konstantin Shvachko updated HADOOP-702:
---------------------------------------

    Attachment: DFSUpgradeProposal2.html

I substantially modified the upgrade proposal.

- There will be more changes in the data layout.
Please let me know if something is not satisfactory. E.g. changing file or 
directory
names will be very hard with backward compatibility and up-/de-gradability in 
mind.

- Taking into account massive layout changes and also that upgrades with 
rollback are 
hard to support for versions with different directory structures, I propose to 
keep automatic 
data conversion (as we had until now) from the current version to the next one. 
No going back (rollback) and force (upgrade) between current and the next 
versions. 
The upgrades will be supported once the data is converted to the new format.
Hope that makes sense.

- The proposal contains more details to cover different failure scenarios.
Like data-node started the upgrade or discard process but crashed before 
completing.

- The discard and the rollback commands are not commands, but rather server 
startup
options. We do not have administrative authorization and this should make 
harder to 
do an upgrade, discard or rollback by mistake.


> DFS Upgrade Proposal
> --------------------
>
>                 Key: HADOOP-702
>                 URL: http://issues.apache.org/jira/browse/HADOOP-702
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Konstantin Shvachko
>         Attachments: DFSUpgradeProposal.html, DFSUpgradeProposal2.html
>
>
> Currently the DFS cluster upgrade procedure is manual.
> http://wiki.apache.org/lucene-hadoop/Hadoop_Upgrade
> It is rather complicated and does not guarantee data recoverability in case 
> of software errors or administrator mistakes.
> This is a description of utilities that make the upgrade process almost 
> automatic and minimize chance of loosing or corrupting data.
> Please see the attached html file for details.

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