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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Reopened] (HDFS-8873) Allow the directoryScanner to be rate-limited
Date Thu, 27 Apr 2017 16:43:05 GMT

     [ https://issues.apache.org/jira/browse/HDFS-8873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Zhe Zhang reopened HDFS-8873:
-----------------------------

> Allow the directoryScanner to be rate-limited
> ---------------------------------------------
>
>                 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
>              Labels: 2.7.2-candidate
>             Fix For: 2.8.0, 3.0.0-alpha1
>
>         Attachments: HDFS-8873.001.patch, HDFS-8873.002.patch, HDFS-8873.003.patch, HDFS-8873.004.patch,
HDFS-8873.005.patch, HDFS-8873.006.patch, HDFS-8873.007.patch, HDFS-8873.008.patch, HDFS-8873.009.patch,
HDFS-8873-branch-2.7.009.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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