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https://issues.apache.org/jira/browse/MAPREDUCE-6166?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14234498#comment-14234498
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Gera Shegalov commented on MAPREDUCE-6166:
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[~eepayne], thanks for your reproducer. Would you mind uploading your patch to
run it through Jenkins. If there is no test catching it, we should add it. Now
it is more clear why we would need the checksum via IFile . Now I feel more
strongly that we need to get rid of the checksumming LocalFileSystem just like
in MapTask.
> Reducers do not catch bad map output transfers during shuffle if data
> shuffled directly to disk
> -----------------------------------------------------------------------------------------------
>
> Key: MAPREDUCE-6166
> URL: https://issues.apache.org/jira/browse/MAPREDUCE-6166
> Project: Hadoop Map/Reduce
> Issue Type: Bug
> Components: mrv2
> Affects Versions: 2.6.0
> Reporter: Eric Payne
> Assignee: Eric Payne
> Attachments: MAPREDUCE-6166.v1.201411221941.txt,
> MAPREDUCE-6166.v2.201411251627.txt
>
>
> In very large map/reduce jobs (50000 maps, 2500 reducers), the intermediate
> map partition output gets corrupted on disk on the map side. If this
> corrupted map output is too large to shuffle in memory, the reducer streams
> it to disk without validating the checksum. In jobs this large, it could take
> hours before the reducer finally tries to read the corrupted file and fails.
> Since retries of the failed reduce attempt will also take hours, this delay
> in discovering the failure is multiplied greatly.
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