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From "Fengdong Yu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-5778) Document new commands and parameters for improved rolling upgrades
Date Sat, 22 Feb 2014 05:58:19 GMT

    [ https://issues.apache.org/jira/browse/HDFS-5778?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13909258#comment-13909258
] 

Fengdong Yu commented on HDFS-5778:
-----------------------------------

[~szetszwo] I have some confusion after read the document.
{code}
+  <subsection name="Upgrade without Downtime" id="UpgradeWithoutDowntime">
+  <p>
+    In a HA cluster, there are two or more NameNodes (NNs), many DataNodes (DNs),
+    a few JournalNodes (JNs) and a few ZooKeeperNodes (ZKNs).
+    Note that JNs and ZKNs are not considered in the upgrade procedure described here.
+    It may incur cluster downtime for upgrading these nodes.
+  </p>
{code}

How to rolling upgrade JNs? if we've upgraded NNs and DNs, then we cannot leave JNs as old.
can you add some descriptions here?
I don't think ZKNs need to upgrade after NNs and DNs are upgraded.

{code}
+    <li>Upgrade DNs<ol>
+      <li>Choose a small subset of datanodes (e.g. all datanodes under a particular
rack).</li>
+      <li>Use <a href="#dfsadminCommands">dfsadmin</a> to shutdown all
the chosen datanodes.
+          Upgrade and restart them.</li>
+      <li>Repeat the above steps until all datanodes in the cluster are upgraded.</li>
+    </ol></li>
{code}

why choose a small subset DNs to upgrade instead of "dfsadmin -rollingUpgrade start" for all
DNs? maybe there are some special reasons omitted?


> 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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