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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3205) Read multiple chunks directly from FSInputChecker subclass into user buffers
Date Fri, 06 Nov 2009 00:49:32 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3205?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12774160#action_12774160
] 

Raghu Angadi commented on HADOOP-3205:
--------------------------------------


I briefly went through the patch. looks fine. will review  soon. It updates readChunk()'s
contract to include multiple chunks. 

Are the DFSClient changes going to be part of a different jira? Let me know if I should do
that.
I think hdfs client's read numbers would as good as slightly better.

> Read multiple chunks directly from FSInputChecker subclass into user buffers
> ----------------------------------------------------------------------------
>
>                 Key: HADOOP-3205
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3205
>             Project: Hadoop Common
>          Issue Type: Bug
>          Components: fs
>            Reporter: Raghu Angadi
>            Assignee: Todd Lipcon
>         Attachments: hadoop-3205.txt, hadoop-3205.txt, hadoop-3205.txt
>
>
> Implementations of FSInputChecker and FSOutputSummer like DFS do not have access to full
user buffer. At any time DFS can access only up to 512 bytes even though user usually reads
with a much larger buffer (often controlled by io.file.buffer.size). This requires implementations
to double buffer data if an implementation wants to read or write larger chunks of data from
underlying storage.
> We could separate changes for FSInputChecker and FSOutputSummer into two separate jiras.

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