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Date: Fri, 25 Jun 2010 21:14:55 -0400 (EDT)
From: "Rodrigo Schmidt (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Subject: [jira] Commented: (HDFS-1094) Intelligent block placement policy to
 decrease probability of block loss
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    [ https://issues.apache.org/jira/browse/HDFS-1094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12882795#action_12882795 ] 

Rodrigo Schmidt commented on HDFS-1094:
---------------------------------------

That might make it hard to start reading, since no context will be given to the reader.

I think Aravind tried to list the whole set of assumptions in the beginning of section 2. Maybe we just have to make it clearer.

> Intelligent block placement policy to decrease probability of block loss
> ------------------------------------------------------------------------
>
>                 Key: HDFS-1094
>                 URL: https://issues.apache.org/jira/browse/HDFS-1094
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: dhruba borthakur
>            Assignee: Rodrigo Schmidt
>         Attachments: prob.pdf, prob.pdf
>
>
> The current HDFS implementation specifies that the first replica is local and the other two replicas are on any two random nodes on a random remote rack. This means that if any three datanodes die together, then there is a non-trivial probability of losing at least one block in the cluster. This JIRA is to discuss if there is a better algorithm that can lower probability of losing a block.

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