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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-988) Namenode should use single map for block to its meta data.
Date Wed, 21 Feb 2007 19:20:06 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12474799
] 

Raghu Angadi commented on HADOOP-988:
-------------------------------------

Proposed chages:

create a new class 'BlockMap' class that internally maps a block to its metadata (currently
INode and containing nodes). This class will provided member functions for various operations
on containingNodes and current accesses to activeBlocks.

This will provide flexibility to use either ArrayList or a java array (saves an ArrayList
object per block) for containing nodes. 



> Namenode should use single map for block to its meta data.
> ----------------------------------------------------------
>
>                 Key: HADOOP-988
>                 URL: https://issues.apache.org/jira/browse/HADOOP-988
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>            Reporter: Raghu Angadi
>         Assigned To: Raghu Angadi
>             Fix For: 0.12.0
>
>
> This is a follow up from HADOOP-803. Currently there two maps which have similar functionality
:
>    1) blockMap : maps block to list of datanodes  that contain the block
>    2) activeBlocks : maps block to INode that it blongs to.
> Apart from simplifying, it saves 32 bytes per block and 24 bytes by avoid extra block
object we currently have for files that exist before Namenode starts (see HADOOP-803).
> We could combine these two into something like block to { containingNodes, INode, etc
}. 
> Another option is to get Move INode and list of dataNodes into Block object.
> Another option that requires bigger change is not use Block object but just 64 bit BlockId.
Then the map would be BlockId to all the block related info. I will file another Jira regd
not using Block object in NameNode.

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