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https://issues.apache.org/jira/browse/HDFS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13050621#comment-13050621
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Todd Lipcon commented on HDFS-941:
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Konstantin:
Yes, everything runs on one node. It tests the localhost path, which is
identical to what would be tested with your proposed benchmark (nrFiles <=
nrNodes means full locality, right?).
bq. Also with 128 MB file everything is in RAM, not sure what it measures
It measures the overhead of DFS rather than the cost of IO. Having it *not* be
in RAM makes for a worse test since differences in CPU overhead are lost in the
noise of the slow disks.
> 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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