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https://issues.apache.org/jira/browse/HDFS-7430?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14286588#comment-14286588
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Tsz Wo Nicholas Sze commented on HDFS-7430:
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> It is fair to call this a rewrite of major parts of the block scanner.
Then, could you reuse the old class and keep the old code you are using so that
it is easier to review?
Since this is not a small patch, how about working this in a branch?
> Rewrite the BlockScanner to use O(1) memory and use multiple threads
> --------------------------------------------------------------------
>
> Key: HDFS-7430
> URL: https://issues.apache.org/jira/browse/HDFS-7430
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.7.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-7430.002.patch, HDFS-7430.003.patch,
> HDFS-7430.004.patch, HDFS-7430.005.patch, HDFS-7430.006.patch,
> HDFS-7430.007.patch, HDFS-7430.008.patch, HDFS-7430.009.patch,
> HDFS-7430.010.patch, HDFS-7430.011.patch, HDFS-7430.012.patch, memory.png
>
>
> We should update the BlockScanner to use a constant amount of memory by
> keeping track of what block was scanned last, rather than by tracking the
> scan status of all blocks in memory. Also, instead of having just one
> thread, we should have a verification thread per hard disk (or other volume),
> scanning at a configurable rate of bytes per second.
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