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https://issues.apache.org/jira/browse/HDFS-1601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12987392#action_12987392
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Todd Lipcon commented on HDFS-1601:
-----------------------------------
Options are to either wrap replyOut with a BufferedOutputStream, or modify
PipelineAck.write() to actually make a byte[] with its reply and call .write()
only once.
I tested the BufferedOutputStream approach on a cluster, and the packet count
went way down. I also saw a noticeable improvement on HBase performance - this
particular benchmark basically tests how fast it can call sync().
> 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
>
>
> 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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