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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-1652) Rebalance data blocks when new data nodes added or data nodes become full
Date Fri, 26 Oct 2007 20:51:50 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-1652?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Hairong Kuang updated HADOOP-1652:
----------------------------------

    Attachment: balancer.patch

A patch for review.

> Rebalance data blocks when new data nodes added or data nodes become full
> -------------------------------------------------------------------------
>
>                 Key: HADOOP-1652
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1652
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: dfs
>    Affects Versions: 0.13.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.16.0
>
>         Attachments: balancer.patch, RebalanceDesign4.pdf, RebalanceDesign5.pdf, RebalanceDesign6.pdf
>
>
> When a new data node joins hdfs cluster, it does not hold much data. So any map task
assigned to the machine most likely does not read local data, thus increasing the use of network
bandwidth. On the other hand, when some data nodes become full, new data blocks are placed
on only non-full data nodes, thus reducing their read parallelism. 
> This jira aims to find an approach to redistribute data blocks when imbalance occurs
in the cluster.  An solution should meet the following requirements:
> 1. It maintains data availablility guranteens in the sense that rebalancing does not
reduce the number of replicas that a block has or the number of racks that the block resides.
> 2. An adminstrator should be able to invoke and interrupt rebalancing from a command
line.
> 3. Rebalancing should be throttled so that rebalancing does not cause a namenode to be
too busy to serve any incoming request or saturate the network.

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