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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-5638) More improvement on block placement performance
Date Thu, 16 Apr 2009 18:21:15 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-5638?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12699791#action_12699791
] 

Suresh Srinivas commented on HADOOP-5638:
-----------------------------------------

+1

Nits - There are several typos {{replca}}, {{datanodesthat}}, {{choosen}}, {{availabe}}, {{tranverses}},
{{relicated}}


> More improvement on block placement performance
> -----------------------------------------------
>
>                 Key: HADOOP-5638
>                 URL: https://issues.apache.org/jira/browse/HADOOP-5638
>             Project: Hadoop Core
>          Issue Type: Improvement
>          Components: dfs
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>             Fix For: 0.21.0
>
>         Attachments: excludedList.patch, excludedList1.patch, excludedList2.patch, excludedList3.patch
>
>
> Block placement algorithm currently has an excluded node list, which contains all datanodes
that have been visited. This list is implemented as an array list, whose cost of inserting
is O(1) but the cost of query "contains" is O( n ), where n is the number of datanodes. This
makes the cost of block placement to be O(n*n) when a cluster is full.
> I propose to change the data structure of the excluded node list as a HashMap. So in
average, the cost of insertion is O(1) and the cost of query is O(1). This makes the block
placement algorithm to be O( n ) in average.

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