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From "Konstantin Shvachko (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-941) Datanode xceiver protocol should allow reuse of a connection
Date Thu, 16 Jun 2011 18:05:49 GMT

    [ https://issues.apache.org/jira/browse/HDFS-941?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13050609#comment-13050609
] 

Konstantin Shvachko commented on HDFS-941:
------------------------------------------

> I think it is reasonable to run tests against the latest patch and make sure there is
no regression in performance.

This is exactly what I asked. That is to run DFSIO on 5-node cluster with and without the
*new* patch.
Here is the command I propose to run for 5 nodes (should have nrFile <= nrNodes).
{code}
TestDFSIO -read -fileSize 10GB -nrFiles 5
{code}
You can run -write first to generate data.
I think this will be representative enough.

> it failed to reject the null hypothesis

Great analysis Todd, I am truly impressed. Does everything run on one node? Is there any inter-DN
communication then? Also with 128 MB file everything is in RAM, not sure what it measures.

> Uncommitting now may do more harm than good.

If my concerns can be addressed without uncommitting then I can hold on to that. Please confirm
somebody is doing it.

> 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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