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https://issues.apache.org/jira/browse/HADOOP-3232?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12593771#action_12593771
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Johan Oskarsson commented on HADOOP-3232:
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If I understand this correctly the purpose of a block report is to let the
namenode know if a block mysteriously goes missing on the data node.
Would it make sense to have this as part of the block verification mechanism
described in HADOOP-2012? Is it already?
That way the block report could always be sent from memory and doesn't have to
hit the disk.
Of course just commenting out the fs scan as Raghu suggest would also work, how
big is the issue of blocks going missing?
> Datanodes time out
> ------------------
>
> Key: HADOOP-3232
> URL: https://issues.apache.org/jira/browse/HADOOP-3232
> Project: Hadoop Core
> Issue Type: Bug
> Components: dfs
> Affects Versions: 0.16.2
> Environment: 10 node cluster + 1 namenode
> Reporter: Johan Oskarsson
> Priority: Critical
> Fix For: 0.18.0
>
> Attachments: du-nonblocking-v1.patch, hadoop-hadoop-datanode-new.log,
> hadoop-hadoop-datanode-new.out, hadoop-hadoop-datanode.out,
> hadoop-hadoop-namenode-master2.out
>
>
> I recently upgraded to 0.16.2 from 0.15.2 on our 10 node cluster.
> Unfortunately we're seeing datanode timeout issues. In previous versions
> we've often seen in the nn webui that one or two datanodes "last contact"
> goes from the usual 0-3 sec to ~200-300 before it drops down to 0 again.
> This causes mild discomfort but the big problems appear when all nodes do
> this at once, as happened a few times after the upgrade.
> It was suggested that this could be due to namenode garbage collection, but
> looking at the gc log output it doesn't seem to be the case.
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