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https://issues.apache.org/jira/browse/HADOOP-3677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12612778#action_12612778
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Raghu Angadi commented on HADOOP-3677:
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I haven't looked at the code around the upgrade or generation stamps yet. I
think the basic fix (or work around) that Konstantin suggesting is to rename
all the metadata files with default generation stamp when Datanode starts
before reporting them to Namenode.
Main advantage I see is that it will avoid extra warnings for every block.
> 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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