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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1114) Reducing NameNode memory usage by an alternate hash table
Date Thu, 03 Jun 2010 00:59:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12874895#action_12874895
] 

Tsz Wo (Nicholas), SZE commented on HDFS-1114:
----------------------------------------------

Thanks Suresh that he found out an interesting post explaining [why java.util.HashMap uses
power of two table length|http://www.roseindia.net/javatutorials/javahashmap.shtml].

> Reducing NameNode memory usage by an alternate hash table
> ---------------------------------------------------------
>
>                 Key: HDFS-1114
>                 URL: https://issues.apache.org/jira/browse/HDFS-1114
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: name-node
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>         Attachments: GSet20100525.pdf
>
>
> NameNode uses a java.util.HashMap to store BlockInfo objects.  When there are many blocks
in HDFS, this map uses a lot of memory in the NameNode.  We may optimize the memory usage
by a light weight hash table implementation.

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