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https://issues.apache.org/jira/browse/HADOOP-3677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12612355#action_12612355
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Konstantin Shvachko commented on HADOOP-3677:
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May be a good solution would be to covert the distributed upgrade into local
data-node upgrade.
It will solve both of the problems above, plus eliminate the warning message
reported in HADOOP-3732.
The only disadvantage of this approach I can see is that data-nodes will take
rather long time to startup, around 5 minutes each on a large cluster.
But this can be solved by including reasonable messages about the upgrade
progress.
> 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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