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https://issues.apache.org/jira/browse/HDFS-630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13096338#comment-13096338
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Suresh Srinivas commented on HDFS-630:
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+1 for the patch.
> In DFSOutputStream.nextBlockOutputStream(), the client can exclude specific
> datanodes when locating the next block.
> -------------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-630
> URL: https://issues.apache.org/jira/browse/HDFS-630
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs client, name-node
> Affects Versions: 0.20-append
> Reporter: Ruyue Ma
> Assignee: Cosmin Lehene
> Fix For: 0.20-append, 0.21.0
>
> Attachments: 0001-Fix-HDFS-630-0.21-svn-1.patch,
> 0001-Fix-HDFS-630-0.21-svn-2.patch, 0001-Fix-HDFS-630-0.21-svn.patch,
> 0001-Fix-HDFS-630-for-0.21-and-trunk-unified.patch,
> 0001-Fix-HDFS-630-for-0.21.patch, 0001-Fix-HDFS-630-svn.patch,
> 0001-Fix-HDFS-630-svn.patch, 0001-Fix-HDFS-630-trunk-svn-1.patch,
> 0001-Fix-HDFS-630-trunk-svn-2.patch, 0001-Fix-HDFS-630-trunk-svn-3.patch,
> 0001-Fix-HDFS-630-trunk-svn-3.patch, 0001-Fix-HDFS-630-trunk-svn-4.patch,
> HDFS-630.20-security.1.patch, HDFS-630.patch, hdfs-630-0.20-append.patch,
> hdfs-630-0.20.txt
>
>
> created from hdfs-200.
> If during a write, the dfsclient sees that a block replica location for a
> newly allocated block is not-connectable, it re-requests the NN to get a
> fresh set of replica locations of the block. It tries this
> dfs.client.block.write.retries times (default 3), sleeping 6 seconds between
> each retry ( see DFSClient.nextBlockOutputStream).
> This setting works well when you have a reasonable size cluster; if u have
> few datanodes in the cluster, every retry maybe pick the dead-datanode and
> the above logic bails out.
> Our solution: when getting block location from namenode, we give nn the
> excluded datanodes. The list of dead datanodes is only for one block
> allocation.
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