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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8486) DN startup may cause severe data loss
Date Wed, 03 Jun 2015 13:36:40 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8486?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14570823#comment-14570823
] 

Hudson commented on HDFS-8486:
------------------------------

FAILURE: Integrated in Hadoop-Mapreduce-trunk-Java8 #215 (See [https://builds.apache.org/job/Hadoop-Mapreduce-trunk-Java8/215/])
HDFS-8486. DN startup may cause severe data loss (Daryn Sharp via Colin P.  McCabe) (cmccabe:
rev 03fb5c642589dec4e663479771d0ae1782038b63)
* hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
* hadoop-hdfs-project/hadoop-hdfs/src/test/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/TestFsDatasetImpl.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/DataNode.java
* hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java


> DN startup may cause severe data loss
> -------------------------------------
>
>                 Key: HDFS-8486
>                 URL: https://issues.apache.org/jira/browse/HDFS-8486
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: datanode
>    Affects Versions: 0.23.1, 2.0.0-alpha
>            Reporter: Daryn Sharp
>            Assignee: Daryn Sharp
>            Priority: Blocker
>             Fix For: 2.7.1
>
>         Attachments: HDFS-8486.patch, HDFS-8486.patch
>
>
> A race condition between block pool initialization and the directory scanner may cause
a mass deletion of blocks in multiple storages.
> If block pool initialization finds a block on disk that is already in the replica map,
it deletes one of the blocks based on size, GS, etc.  Unfortunately it _always_ deletes one
of the blocks even if identical, thus the replica map _must_ be empty when the pool is initialized.
> The directory scanner starts at a random time within its periodic interval (default 6h).
 If the scanner starts very early it races to populate the replica map, causing the block
pool init to erroneously delete blocks.



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