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https://issues.apache.org/jira/browse/HDFS-903?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12923255#action_12923255
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Konstantin Shvachko commented on HDFS-903:
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Hairong, we should also add the image MD5 digest into CheckpointSignature. I
believe it will be easier to do that if the digest is in VERSION. Also until
VERSION is written it does not matter what the image state is. If VERSION is
written then the MD5 is there so everything is consistent.
Would you consider adding MD5 into CheckpointSignature?
> 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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