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Date: Tue, 8 Feb 2011 05:47:57 +0000 (UTC)
From: "Tsz Wo (Nicholas), SZE (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
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Subject: [jira] Commented: (HDFS-1601) Pipeline ACKs are sent as lots of
 tiny TCP packets
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    [ https://issues.apache.org/jira/browse/HDFS-1601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12991808#comment-12991808 ] 

Tsz Wo (Nicholas), SZE commented on HDFS-1601:
----------------------------------------------

Hi Todd, using two {{BufferedOutputStream}}s does not sound right.  I think the problem may be in SMALL_BUFFER_SIZE.  Do you know what value was it in your test?

> Pipeline ACKs are sent as lots of tiny TCP packets
> --------------------------------------------------
>
>                 Key: HDFS-1601
>                 URL: https://issues.apache.org/jira/browse/HDFS-1601
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: data-node
>    Affects Versions: 0.22.0
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>             Fix For: 0.22.0
>
>         Attachments: hdfs-1601.txt
>
>
> I noticed in an hbase benchmark that the packet counts in my network monitoring seemed high, so took a short pcap trace and found that each pipeline ACK was being sent as five packets, the first four of which only contain one byte. We should buffer these bytes and send the PipelineAck as one TCP packet.

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