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https://issues.apache.org/jira/browse/HDFS-8873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Templeton updated HDFS-8873:
-----------------------------------
    Target Version/s: 2.8.0

> throttle directoryScanner
> -------------------------
>
>                 Key: HDFS-8873
>                 URL: https://issues.apache.org/jira/browse/HDFS-8873
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 2.7.1
>            Reporter: Nathan Roberts
>            Assignee: Daniel Templeton
>
> 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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