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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-6758) block writer should pass the expected block size to DataXceiverServer
Date Mon, 28 Jul 2014 18:04:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-6758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14076492#comment-14076492

Colin Patrick McCabe commented on HDFS-6758:

I apologize if this is a dumb question, but how would the writer pass the expected block size
to the DN?  Via datatransferprotocol?

> block writer should pass the expected block size to DataXceiverServer
> ---------------------------------------------------------------------
>                 Key: HDFS-6758
>                 URL: https://issues.apache.org/jira/browse/HDFS-6758
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode, hdfs-client
>    Affects Versions: 2.4.1
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
> DataXceiver initializes the block size to the default block size for the cluster. This
size is later used by the FsDatasetImpl when applying VolumeChoosingPolicy.
> {code}
>     block.setNumBytes(dataXceiverServer.estimateBlockSize);
> {code}
> where
> {code}
>   /**
>    * We need an estimate for block size to check if the disk partition has
>    * enough space. For now we set it to be the default block size set
>    * in the server side configuration, which is not ideal because the
>    * default block size should be a client-size configuration. 
>    * A better solution is to include in the header the estimated block size,
>    * i.e. either the actual block size or the default block size.
>    */
>   final long estimateBlockSize;
> {code}
> In most cases the writer can just pass the maximum expected block size to the DN instead
of having to use the cluster default.

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