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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1034) Enhance datanode to read data and checksum file in parallel
Date Thu, 11 Mar 2010 20:56:27 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844232#action_12844232

Todd Lipcon commented on HDFS-1034:

A bit of manual readahead on the checksum file could theoretically have the same benefit without
the problem Jay mentioned. The Checksum file is opened with a buffer, right? In that case,
do we expect to see a big benefit?

> Enhance datanode to read data and checksum file in parallel
> -----------------------------------------------------------
>                 Key: HDFS-1034
>                 URL: https://issues.apache.org/jira/browse/HDFS-1034
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
> In the current HDFS implementation, a read of a block issued to the datanode results
in a disk access to the checksum file followed by a disk access to the checksum file. It would
be nice to be able to do these two IOs in parallel to reduce read latency.

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