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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3875) Issue handling checksum errors in write pipeline
Date Wed, 28 Nov 2012 01:36:59 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13505151#comment-13505151
] 

Tsz Wo (Nicholas), SZE commented on HDFS-3875:
----------------------------------------------

> ... Nicholas, any comments on if this applies to old pipeline vs new pipeline?

Both the old and the new pipelines should have the similar problem since, when machine A sends
some data to machine B and it fails, it is generally impossible to detect whether A, B or
the network is faulty.  Of course, we can detect it for some special cases such as one of
the machine dead.

> Potential blocker for 2.0.3-alpha.

I would say that this is not a blocker for 2.0.3-alpha since this is not a regression.
                
> Issue handling checksum errors in write pipeline
> ------------------------------------------------
>
>                 Key: HDFS-3875
>                 URL: https://issues.apache.org/jira/browse/HDFS-3875
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node, hdfs client
>    Affects Versions: 2.0.2-alpha
>            Reporter: Todd Lipcon
>            Assignee: Kihwal Lee
>            Priority: Blocker
>
> We saw this issue with one block in a large test cluster. The client is storing the data
with replication level 2, and we saw the following:
> - the second node in the pipeline detects a checksum error on the data it received from
the first node. We don't know if the client sent a bad checksum, or if it got corrupted between
node 1 and node 2 in the pipeline.
> - this caused the second node to get kicked out of the pipeline, since it threw an exception.
The pipeline started up again with only one replica (the first node in the pipeline)
> - this replica was later determined to be corrupt by the block scanner, and unrecoverable
since it is the only replica

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