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https://issues.apache.org/jira/browse/HDFS-6800?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14114306#comment-14114306
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Arpit Agarwal edited comment on HDFS-6800 at 8/28/14 8:38 PM:
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James, would it be simpler to just fix {{NameNodeRpcServer.blockReport}} to 
return FinalizeCommand only if {{namesystem.isRollingUpgrade}} returns false or 
is there some other implication of leaving {{isUpgradeFinalized}} to false that 
I am not thinking of?


was (Author: arpitagarwal):
James, would it be simpler to just fix {{NameNodeRpcServer.blockReport}} to 
FinalizeCommand only if {{namesystem.isRollingUpgrade}} returns false or is 
there some other implication of leaving {{isUpgradeFinalized}} to false that I 
am not thinking of?

> 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.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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