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Date: Fri, 11 Sep 2015 19:08:47 +0000 (UTC)
From: "Daniel Templeton (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12852998.1438965546000.317908.1441998527611@Atlassian.JIRA>
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Subject: [jira] [Updated] (HDFS-8873) throttle directoryScanner
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     [ https://issues.apache.org/jira/browse/HDFS-8873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Daniel Templeton updated HDFS-8873:
-----------------------------------
    Status: Patch Available  (was: Open)

> 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
>
>
> 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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