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Date: Thu, 16 Jun 2011 20:58:47 +0000 (UTC)
From: "dhruba borthakur (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] [Commented] (HDFS-941) Datanode xceiver protocol should
 allow reuse of a connection
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    [ https://issues.apache.org/jira/browse/HDFS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13050726#comment-13050726 ] 

dhruba borthakur commented on HDFS-941:
---------------------------------------

My experience with TestDFSIO has been that the variance of its results are higher (especially due to map-reduce software scheduling), and could never capture (at least, for me) small differences in performance of DFS.

> Datanode xceiver protocol should allow reuse of a connection
> ------------------------------------------------------------
>
>                 Key: HDFS-941
>                 URL: https://issues.apache.org/jira/browse/HDFS-941
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node, hdfs client
>    Affects Versions: 0.22.0
>            Reporter: Todd Lipcon
>            Assignee: bc Wong
>             Fix For: 0.22.0
>
>         Attachments: 941.22.txt, 941.22.txt, 941.22.v2.txt, 941.22.v3.txt, HDFS-941-1.patch, HDFS-941-2.patch, HDFS-941-3.patch, HDFS-941-3.patch, HDFS-941-4.patch, HDFS-941-5.patch, HDFS-941-6.22.patch, HDFS-941-6.patch, HDFS-941-6.patch, HDFS-941-6.patch, fix-close-delta.txt, hdfs-941.txt, hdfs-941.txt, hdfs-941.txt, hdfs-941.txt, hdfs941-1.png
>
>
> Right now each connection into the datanode xceiver only processes one operation.
> In the case that an operation leaves the stream in a well-defined state (eg a client reads to the end of a block successfully) the same connection could be reused for a second operation. This should improve random read performance significantly.

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