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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8453) Erasure coding: properly handle start offset for internal blocks in a block group
Date Tue, 02 Jun 2015 23:17:50 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8453?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14569964#comment-14569964
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Zhe Zhang commented on HDFS-8453:
---------------------------------

Thanks Jing!

> Erasure coding: properly handle start offset for internal blocks in a block group
> ---------------------------------------------------------------------------------
>
>                 Key: HDFS-8453
>                 URL: https://issues.apache.org/jira/browse/HDFS-8453
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Zhe Zhang
>            Assignee: Zhe Zhang
>             Fix For: HDFS-7285
>
>         Attachments: HDFS-8453-HDFS-7285.00.patch, HDFS-8453-HDFS-7285.01.patch
>
>
> {code}
>   void actualGetFromOneDataNode(final DNAddrPair datanode,
>     ...
>       LocatedBlock block = getBlockAt(blockStartOffset);
>     ...
>       fetchBlockAt(block.getStartOffset());
> {code}
> The {{blockStartOffset}} here is from inner block. For parity blocks, the offset will
overlap with the next block group, and we may end up with fetching wrong block. So we have
to assign a meaningful start offset for internal blocks in a block group, especially for parity
blocks.



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