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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3875) Issue handling checksum errors in write pipeline
Date Tue, 27 Nov 2012 18:27:58 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3875?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13504816#comment-13504816
] 

Todd Lipcon commented on HDFS-3875:
-----------------------------------

Thanks for looking into this, Kihwal. Your analysis makes sense to me.

Arun - not sure this should be a blocker - while it's a nasty corruption issue, I don't think
it's anything new. AFAIK the write pipeline has always had this issue since the ancient days,
right? Or did the HDFS-265 rewrite end up changing the order of the ack send and the CRC verification?
                
> 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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