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https://issues.apache.org/jira/browse/HDFS-8873?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14804279#comment-14804279
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Daniel Templeton commented on HDFS-8873:
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[sigh] Those tests pass for me locally, so can't say why they failed.
The whitespace error is interesting. I changed line n in the patch. Jenkins
complained about the whitespace on line n+1. I fixed the whitespace on line
n+1 in the next patch. Jenkins is now complaining about the whitespace on line
n+2. There is no issue on line n+3, so I could correct n+2 and be done, but at
that point I've made whitespace changes on two lines that I didn't otherwise
touch. What's the accepted why to do it? Fix the whitespace or ignore the
error?
> throttle directoryScanner
> -------------------------
>
> Key: HDFS-8873
> URL: https://issues.apache.org/jira/browse/HDFS-8873
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 2.7.1
> Reporter: Nathan Roberts
> Assignee: Daniel Templeton
> Attachments: HDFS-8873.001.patch, HDFS-8873.002.patch,
> HDFS-8873.003.patch
>
>
> The new 2-level directory layout can make directory scans expensive in terms
> of disk seeks (see HDFS-8791) for details.
> It would be good if the directoryScanner() had a configurable duty cycle that
> would reduce its impact on disk performance (much like the approach in
> HDFS-8617).
> Without such a throttle, disks can go 100% busy for many minutes at a time
> (assuming the common case of all inodes in cache but no directory blocks
> cached, 64K seeks are required for full directory listing which translates to
> 655 seconds)
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