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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 Tue, 20 Mar 2007 20:16:32 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12482512
] 

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

> Please don't use inheritance for this. It creates lots of confusion. Please create a
field that is the Block.
This is what current patch does.

I am planning to keep the inheritance hidden, just like how current BlockInfo is inside BlocksMap.
Only advantage of inheritance is that it will further reduce the memory per block by 16 bytes.



> 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
>         Attachments: HADOOP-988-1.patch
>
>
> 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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