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https://issues.apache.org/jira/browse/HDFS-5153?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13885006#comment-13885006
 ] 

Hadoop QA commented on HDFS-5153:
---------------------------------

{color:green}+1 overall{color}.  Here are the results of testing the latest 
attachment 
  http://issues.apache.org/jira/secure/attachment/12625769/HDFS-5153.05.patch
  against trunk revision .

    {color:green}+1 @author{color}.  The patch does not contain any @author 
tags.

    {color:green}+1 tests included{color}.  The patch appears to include 4 new 
or modified test files.

    {color:green}+1 javac{color}.  The applied patch does not increase the 
total number of javac compiler warnings.

    {color:green}+1 javadoc{color}.  The javadoc tool did not generate any 
warning messages.

    {color:green}+1 eclipse:eclipse{color}.  The patch built with 
eclipse:eclipse.

    {color:green}+1 findbugs{color}.  The patch does not introduce any new 
Findbugs (version 1.3.9) warnings.

    {color:green}+1 release audit{color}.  The applied patch does not increase 
the total number of release audit warnings.

    {color:green}+1 core tests{color}.  The patch passed unit tests in 
hadoop-hdfs-project/hadoop-hdfs.

    {color:green}+1 contrib tests{color}.  The patch passed contrib unit tests.

Test results: 
https://builds.apache.org/job/PreCommit-HDFS-Build/5971//testReport/
Console output: https://builds.apache.org/job/PreCommit-HDFS-Build/5971//console

This message is automatically generated.

> Datanode should send block reports for each storage in a separate message
> -------------------------------------------------------------------------
>
>                 Key: HDFS-5153
>                 URL: https://issues.apache.org/jira/browse/HDFS-5153
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 3.0.0
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
>         Attachments: HDFS-5153.01.patch, HDFS-5153.03.patch, 
> HDFS-5153.03b.patch, HDFS-5153.04.patch, HDFS-5153.05.patch
>
>
> When the number of blocks on the DataNode grows large we start running into a 
> few issues:
> # Block reports take a long time to process on the NameNode. In testing we 
> have seen that a block report with 6 Million blocks takes close to one second 
> to process on the NameNode. The NameSystem write lock is held during this 
> time.
> # We start hitting the default protobuf message limit of 64MB somewhere 
> around 10 Million blocks. While we can increase the message size limit it 
> already takes over 7 seconds to serialize/unserialize a block report of this 
> size.
> HDFS-2832 has introduced the concept of a DataNode as a collection of 
> storages i.e. the NameNode is aware of all the volumes (storage directories) 
> attached to a given DataNode. This makes it easy to split block reports from 
> the DN by sending one report per storage directory to mitigate the above 
> problems.



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