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https://issues.apache.org/jira/browse/HADOOP-4995?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12662411#action_12662411
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Brian Bockelman commented on HADOOP-4995:
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Hey Konstantin, Dhruba,
I think we're approximately on the same page. The best thing would be to
verify image correctness is the namenode itself. I believe Dhruba expressed
this most succinctly: the "offline fsImage verification" could simply be a
"-checkimage" flag where the namenode would load the fsImage / edits, then exit
0 if nothing bad happened and exit 1 if there was some error.
I wasn't proposing a completely separate tool to verify an image for the
reasons Konstantin pointed out - the only sane way to verify the image is
usable is by the namenode is to use the namenode itself; it'd be impossible to
try and sync two separate implementations.
> Offline Namenode fsImage verification
> -------------------------------------
>
> Key: HADOOP-4995
> URL: https://issues.apache.org/jira/browse/HADOOP-4995
> Project: Hadoop Core
> Issue Type: New Feature
> Components: dfs
> Reporter: Brian Bockelman
>
> Currently, there is no way to verify that a copy of the fsImage is not
> corrupt. I propose that we should have an offline tool that loads the
> fsImage into memory to see if it is usable. This will allow us to automate
> backup testing to some extent.
> One can start a namenode process on the fsImage to see if it can be loaded,
> but this is not easy to automate.
> To use HDFS in production, it is greatly desired to have both checkpoints -
> and have some idea that the checkpoints are valid! No one wants to see the
> day where they reload from backup only to find that the fsImage in the backup
> wasn't usable.
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