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https://issues.apache.org/jira/browse/HDFS-903?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12923567#action_12923567
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Allen Wittenauer commented on HDFS-903:
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> I think it's better to put in VERSION file since then you can use a command
> line "md5sum" utility to check for corruption.
+1
This is much more operations friendly. If an alternative is picked--which is
fine--just keep in mind we'll need a tool built to go with this change.
> NN should verify images and edit logs on startup
> ------------------------------------------------
>
> Key: HDFS-903
> URL: https://issues.apache.org/jira/browse/HDFS-903
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Reporter: Eli Collins
> Assignee: Hairong Kuang
> Priority: Critical
> Fix For: 0.22.0
>
>
> I was playing around with corrupting fsimage and edits logs when there are
> multiple dfs.name.dirs specified. I noticed that:
> * As long as your corruption does not make the image invalid, eg changes an
> opcode so it's an invalid opcode HDFS doesn't notice and happily uses a
> corrupt image or applies the corrupt edit.
> * If the first image in dfs.name.dir is "valid" it replaces the other copies
> in the other name.dirs, even if they are different, with this first image, ie
> if the first image is actually invalid/old/corrupt metadata than you've lost
> your valid metadata, which can result in data loss if the namenode garbage
> collects blocks that it thinks are no longer used.
> How about we maintain a checksum as part of the image and edit log and check
> those on startup and refuse to startup if they are different. Or at least
> provide a configuration option to do so if people are worried about the
> overhead of maintaining checksums of these files. Even if we assume
> dfs.name.dir is reliable storage this guards against operator errors.
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