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https://issues.apache.org/jira/browse/HADOOP-13738?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16464212#comment-16464212
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Kihwal Lee commented on HADOOP-13738:
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We are seeing issues in 2.8 with this change.
- When space is low, the os returns ENOSPC. Instead simply stop writing, the
drive is marked bad and replication happens. This make cluster-wide space
problem worse. If the number of "failed" drives exceeds the DFIP limit, the
datanode shuts down.
- There are non-hdfs users of DiskChecker, who use it proactively, not just on
failures. This was fine before, but now it incurs heavy I/O due to introduction
of fsync() in the code.
> 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
> Priority: Major
> Fix For: 2.9.0, 3.0.0-alpha2, 2.8.4
>
> Attachments: HADOOP-13738-branch-2.8-06.patch, HADOOP-13738.01.patch,
> HADOOP-13738.02.patch, HADOOP-13738.03.patch, HADOOP-13738.04.patch,
> HADOOP-13738.05.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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