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https://issues.apache.org/jira/browse/HADOOP-3677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12612923#action_12612923
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dhruba borthakur commented on HADOOP-3677:
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Changing the distributed -upgrade to a local upgrade sounds ok (though not very
essential) to me. It seems to be another hack: the real problem being that the
distributed framework do not yet have a mechanism to specify that "do not send
block reports before distributed upgrade is complete".
Another alternative would be to keep the namenode in safemode till distributed
upgrade is complete.... isn't this already true today?
> Problems with generation stamp upgrade
> --------------------------------------
>
> Key: HADOOP-3677
> URL: https://issues.apache.org/jira/browse/HADOOP-3677
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.18.0
> Reporter: Konstantin Shvachko
> Assignee: dhruba borthakur
> Priority: Blocker
> Fix For: 0.18.0
>
>
> # The generation stamp upgrade renames blocks' meta-files so that the name
> contains the block generation stamp as stated in HADOOP-2656.
> If a data-node has blocks that do not belong to any files and the name-node
> asks the data-node to remove those blocks
> during or before the upgrade started the data-node will remove the blocks but
> not the meta-files because their names
> are still in the old format which is not recognized by the new code. So we
> can end up with a number of garbage files which
> will be hard to recognize that they are unused and the system will never
> remove them automatically.
> I think this should be handled by the upgrade code in the end, but may be it
> will be right to fix HADOOP-3002 for the 0.18 release,
> which will avoid scheduling block removal when the name-node is in safe-mode.
> # I was not able to get the upgrade -force option to work. This option lets
> the name-node proceed with a distributed upgrade even if
> the data-nodes are not able to complete their local upgrades. Did we test
> this feature at all for the generation stamp upgrade?
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