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Date: Tue, 27 Feb 2007 13:40:05 -0800 (PST)
From: "Hairong Kuang (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Updated: (HADOOP-972) Improve the rack-aware replica
 placement performance
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     [ https://issues.apache.org/jira/browse/HADOOP-972?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hairong Kuang updated HADOOP-972:
---------------------------------

    Status: Open  (was: Patch Available)

> Improve the rack-aware replica placement performance
> ----------------------------------------------------
>
>                 Key: HADOOP-972
>                 URL: https://issues.apache.org/jira/browse/HADOOP-972
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.11.0
>            Reporter: Hairong Kuang
>         Assigned To: Hairong Kuang
>             Fix For: 0.12.0
>
>         Attachments: rack_performance.patch, rack_performance2.patch, rack_performance3.patch
>
>
> This issue aims to improve the rack-aware replica placement performance. A major idea is to avoid constructing lists of possible targets for random selection in chooseTarget, which currently needs interating all DatanodeDescriptors. I plan to change the NetworkTopology data structure as follow:
> 1. each InnerNode stores its childrens as a list;
> 2. each InnerNode adds a new field numberOfLeaves the total number of leaves (i.e. data nodes) in its subtree. 
> NetworkTopology will support two new methods:
> 1. DatanodeDescriptor chooseRandom( String scope): it randomly choose one leave from scope.
> 2. DatanodeDescriptor chooseRandomExclude(String excludedScope): it randomly choose one leave from ~scope
> In addition, Issue 971 will also help improve the performance of the rack-aware DFS patch.

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