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From "Virajith Jalaparti (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-15292) Distcp's use of pread is slowing it down.
Date Wed, 07 Mar 2018 02:35:00 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-15292?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Virajith Jalaparti updated HADOOP-15292:
----------------------------------------
    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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