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Date: Thu, 28 Aug 2014 23:57:08 +0000 (UTC)
From: "Arpit Agarwal (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12731235.1406852925284.5510.1409270228975@arcas>
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References: <JIRA.12731235.1406852925284@arcas>
Subject: [jira] [Commented] (HDFS-6800) Determine how Datanode layout
 changes should interact with rolling upgrade
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    [ https://issues.apache.org/jira/browse/HDFS-6800?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14114619#comment-14114619 ] 

Arpit Agarwal commented on HDFS-6800:
-------------------------------------

Will do once Jenkins +1s the v8 patch.

> Determine how Datanode layout changes should interact with rolling upgrade
> --------------------------------------------------------------------------
>
>                 Key: HDFS-6800
>                 URL: https://issues.apache.org/jira/browse/HDFS-6800
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>    Affects Versions: 2.6.0
>            Reporter: Colin Patrick McCabe
>            Assignee: James Thomas
>         Attachments: HDFS-6800.2.patch, HDFS-6800.3.patch, HDFS-6800.4.patch, HDFS-6800.5.patch, HDFS-6800.6.patch, HDFS-6800.7.patch, HDFS-6800.8.patch, HDFS-6800.patch
>
>
> We need to handle attempts to rolling-upgrade the DataNode to a new storage directory layout.
> One approach is to disallow such upgrades.  If we choose this approach, we should make sure that the system administrator gets a helpful error message and a clean failure when trying to use rolling upgrade to a version that doesn't support it.  Based on the compatibility guarantees described in HDFS-5535, this would mean that *any* future DataNode layout changes would require a major version upgrade.
> Another approach would be to support rolling upgrade from an old DN storage layout to a new layout.  This approach requires us to change our documentation to explain to users that they should supply the {{\-rollback}} command on the command-line when re-starting the DataNodes during rolling rollback.  Currently the documentation just says to restart the DataNode normally.
> Another issue here is that the DataNode's usage message describes rollback options that no longer exist.  The help text says that the DN supports {{\-rollingupgrade rollback}}, but this option was removed by HDFS-6005.


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