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From "Kihwal Lee (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11187) Optimize disk access for last partial chunk checksum of Finalized replica
Date Thu, 01 Feb 2018 15:51:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16348782#comment-16348782

Kihwal Lee commented on HDFS-11187:

The patch looks good to me.

> Optimize disk access for last partial chunk checksum of Finalized replica
> -------------------------------------------------------------------------
>                 Key: HDFS-11187
>                 URL: https://issues.apache.org/jira/browse/HDFS-11187
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode
>            Reporter: Wei-Chiu Chuang
>            Assignee: Wei-Chiu Chuang
>            Priority: Major
>         Attachments: HDFS-11187.001.patch, HDFS-11187.002.patch, HDFS-11187.003.patch,
HDFS-11187.004.patch, HDFS-11187.005.patch
> The patch at HDFS-11160 ensures BlockSender reads the correct version of metafile when
there are concurrent writers.
> However, the implementation is not optimal, because it must always read the last partial
chunk checksum from disk while holding FsDatasetImpl lock for every reader. It is possible
to optimize this by keeping an up-to-date version of last partial checksum in-memory and reduce
disk access.
> I am separating the optimization into a new jira, because maintaining the state of in-memory
checksum requires a lot more work.

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