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https://issues.apache.org/jira/browse/HDFS-1034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844272#action_12844272
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Zlatin Balevsky commented on HDFS-1034:
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The only possible bottleneck is the extra disk seek which may or may not be a
big deal. Probably for HBase-type workloads. There are many ways around that
including but not limited to:
a) prepending a copy of the checksum file to the block file while keeping the
separate copy intact for off-thread verification after the transfer starts
b) using some ext4-extents jni magic
... ?
> 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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