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From "Akshay Nehe (Jira)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-16899) Update HdfsDesign.md to reduce ambiguity
Date Tue, 03 Mar 2020 03:36:00 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-16899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17049868#comment-17049868

Akshay Nehe commented on HADOOP-16899:

Based on comment by [~aajisaka] on the PR, considering replacing the line with:

_Two replicas are on one rack, and the remaining replica is on one of the other racks._

instead of previously indicated update.

An additional recommended update will be included for the sentence 2 sentences before the
previously mentioned.

Quoting Akira:

The following sentence is not directly related to your PR, however, it can be fixed at the
same time.
{quote}However, it does reduce the aggregate network bandwidth used when reading data since
a block is placed in only two unique racks rather than three. With this policy, the replicas
of a file do not evenly distribute across the racks.
{quote} * it does reduce -> it does not reduce

If a block is placed in three unique racks, the probability of rack-local read will increase
and the network bandwidth will be reduced when reading the data. Therefore I think 'does'
should be changed to 'does not'.


Once decided to make both changes, will update the Jira Description.

> Update HdfsDesign.md to reduce ambiguity
> ----------------------------------------
>                 Key: HADOOP-16899
>                 URL: https://issues.apache.org/jira/browse/HADOOP-16899
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: documentation
>            Reporter: Akshay Nehe
>            Priority: Minor
> A proposed update to [https://github.com/apache/hadoop/blob/trunk/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md|http://example.com/] in
the section "Replica Placement: The First Baby Steps" 4th paragraph, 2nd last line.
> The sentence is leading to ambiguity of reader.
> Considering the statement segmented in 3 parts by the commas:
>  # the first part talks about "one thirds of replicas";
>  # the second part talks about "two thirds of replicas"
>  # the third part talking about "the other third" is leading to ambiguity when one thirds
and two thirds have already accounted for the whole.
> Proposed solution:
> Getting rid of the third part or rephrasing entire sentence to capture the overall essence
of the sentence.
> In other words, replacing 
> _One third of replicas are on one node, two thirds of replicas are on one rack, and the
other third are evenly distributed across the remaining racks._
> with
> _One third of replicas are on one node, two thirds of replicas are on one rack._
> Please suggest if any additional meaning is getting lost with this replacement.

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