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https://issues.apache.org/jira/browse/HDFS-903?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12923315#action_12923315
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dhruba borthakur commented on HDFS-903:
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I agree with Konstantin/Hairong that the MD5 signature should be part of the
CheckpointSignature.
It would have been nice if the contents of the VERSION file was stored as a
header record in the beginning of the fsimage file itself (I now remember the
initial reason why the VERSION file exists separate from the fsimage: the
datanode needs the VERSION file too for its block-directories and the datanode
does not have a fsimage file). Given that, t should be fine to store the
checkum in the VERSION file. Also, the algoritm to compute the checksum need
not be configurable, it could be hardcoded to generate a MD5 checksum.
> 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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