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https://issues.apache.org/jira/browse/HDFS-5778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13909551#comment-13909551
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Tsz Wo (Nicholas), SZE commented on HDFS-5778:
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> How to rolling upgrade JNs? if we've upgraded NNs and DNs, then we cannot
> leave JNs as old. ...
Actually, we can leave JNs running old version since JN code is quite
independent other code in HDFS. We might as well move JNs out as a HDFS
sub-project in the future. Let me clarify it in the doc.
> I don't think ZKNs need to upgrade after NNs and DNs are upgraded. ...
Agree. Upgrading ZK is outside the scope of this doc. I just mention it since
a HA cluster require ZK.
> why choose a small subset DNs to upgrade instead of "dfsadmin -rollingUpgrade
> start" for all DNs? maybe there are some special reasons omitted?
"dfsadmin -rollingUpgrade start" is for starting the entire rolling upgrade
process. Then, we need to shutdown, install new software and restart each NN
and DN daemon. Obviously, we don't want to shutdown all DNs since it incurs
downtime.
Thanks for taking a look.
> Document new commands and parameters for improved rolling upgrades
> ------------------------------------------------------------------
>
> Key: HDFS-5778
> URL: https://issues.apache.org/jira/browse/HDFS-5778
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: documentation
> Affects Versions: HDFS-5535 (Rolling upgrades)
> Reporter: Akira AJISAKA
> Assignee: Tsz Wo (Nicholas), SZE
> Attachments: h5778_20140220.patch, h5778_20140221.patch
>
>
> "hdfs dfsadmin -rollingUpgrade" command was newly added in HDFS-5752, and
> some other commands and parameters will be added in the future. This issue
> exists to flag undocumented commands and parameters when HDFS-5535 branch is
> merging to trunk.
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