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https://issues.apache.org/jira/browse/HADOOP-13738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15606082#comment-15606082
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Arpit Agarwal commented on HADOOP-13738:
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[~kihwal] that's a good point. The caller should deal with slow checks since a 
single check can also hang indefinitely. The DN currently serializes disk 
checks so one slow disk can delay checking the rest. Also it doesn't handle 
stalled checks. I am testing some changes to fix this in the DataNode and plan 
to post patches in the next few days.

> DiskChecker should perform some disk IO
> ---------------------------------------
>
>                 Key: HADOOP-13738
>                 URL: https://issues.apache.org/jira/browse/HADOOP-13738
>             Project: Hadoop Common
>          Issue Type: Improvement
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
>         Attachments: HADOOP-13738.01.patch, HADOOP-13738.02.patch, 
> HADOOP-13738.03.patch
>
>
> DiskChecker can fail to detect total disk/controller failures indefinitely. 
> We have seen this in real clusters. DiskChecker performs simple 
> permissions-based checks on directories which do not guarantee that any disk 
> IO will be attempted.
> A simple improvement is to write some data and flush it to the disk.



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