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https://issues.apache.org/jira/browse/HDFS-1034?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12844285#action_12844285
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Todd Lipcon commented on HDFS-1034:
-----------------------------------
In practice I don't imagine the extra disk seek for checksums is a problem for
HBase - since the checksum file is relatively small, my guess is that it stays
hot in the linux buffer cache and therefore doesn't represent any disk access.
Would certainly be interesting to run blktrace on a heavily loaded hbase
datanode to see if this is true, though!
> 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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