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From "lohit vijayarenu (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3392) Corrupted blocks leading to job failures
Date Wed, 21 May 2008 20:29:55 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3392?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12598777#action_12598777
] 

lohit vijayarenu commented on HADOOP-3392:
------------------------------------------

Ok, so the above steps basically re-computes checksum on all blocks of the file. Your suggestion
about salvaging (re-computing checksum in this case) for truncated block sounds like a good
option to have. 
There could be 2 ways to solve this. Recompute checksum for whole file or do it just for corrupt
block. If we do the second option, we might end up having blocks of size less than BLOCK_SIZE
in the system. 

> Corrupted blocks leading to job failures
> ----------------------------------------
>
>                 Key: HADOOP-3392
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3392
>             Project: Hadoop Core
>          Issue Type: Improvement
>    Affects Versions: 0.16.0
>            Reporter: Christian Kunz
>
> On one of our clusters we ended up with 11 singly-replicated corrupted blocks (checksum
errors) such that jobs were failing because of no live blocks available.
> fsck reports the system as healthy, although it is not.
> I argue that fsck should have an option to check whether under-replicated blocks are
okay.
> Even better, the namenode should automatically check under-replicated blocks with repeated
replication failures for corruption and list them somewhere on the GUI. And for checksum errors,
there should be an option to undo the corruption and recompute the checksums.
> Question: Is it at all probable that two or more replications of a block have checksum
errors? If not, then we could reduce the checking to singly-replicated blocks.

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