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https://issues.apache.org/jira/browse/HADOOP-15292?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Virajith Jalaparti updated HADOOP-15292:
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Description: Distcp currently uses positioned-reads (in
RetriableFileCopyCommand#copyBytes) when the source offset is > 0. This results
in unnecessary overheads (new BlockReader being created on the client-side,
multiple readBlock() calls to the Datanodes, each of which requires the
creation of a BlockSender and an inputstream to the ReplicaInfo). (was: Distcp
currently uses positioned-reads (in RetriableFileCopyCommand#copyBytes) when
the source offset is > 0. This results in unnecessary overheads (new
BlockReader being created on the client-side, multiple readBlock() calls to the
Datanodes, each of requires the creation of a BlockSender and an inputstream to
the ReplicaInfo).)
> Distcp's use of pread is slowing it down.
> -----------------------------------------
>
> Key: HADOOP-15292
> URL: https://issues.apache.org/jira/browse/HADOOP-15292
> Project: Hadoop Common
> Issue Type: Bug
> Components: tools/distcp
> Affects Versions: 3.0.0
> Reporter: Virajith Jalaparti
> Priority: Minor
> Attachments: HADOOP-15292.000.patch
>
>
> Distcp currently uses positioned-reads (in
> RetriableFileCopyCommand#copyBytes) when the source offset is > 0. This
> results in unnecessary overheads (new BlockReader being created on the
> client-side, multiple readBlock() calls to the Datanodes, each of which
> requires the creation of a BlockSender and an inputstream to the ReplicaInfo).
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