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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8020) Erasure Coding: restore BlockGroup and schema info from stripping coding command
Date Fri, 03 Apr 2015 21:22:52 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8020?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14395102#comment-14395102
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Zhe Zhang commented on HDFS-8020:
---------------------------------

I think the command is just to reconstruct a lost data in the group, which can be either raw
or parity. In a generic scenario, we might even construct both a raw data block and a parity
data blocks through the same command. [~drankye] What 4 cases do you have in mind?

bq. Right. But we do have the class already (in the branch), or anything more other than it
did you mean?
Sorry I meant HDFS-7859. We need to represent ECSchemas in NN, and then we can serialize and
transfer the ECSchema to DN in a reconstruction command.

> Erasure Coding: restore BlockGroup and schema info from stripping coding command
> --------------------------------------------------------------------------------
>
>                 Key: HDFS-8020
>                 URL: https://issues.apache.org/jira/browse/HDFS-8020
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Kai Sasaki
>
> As a task of HDFS-7344, to process *stripping* coding commands from NameNode or other
scheduler services/tools, we need to first be able to restore BlockGroup and schema information
in DataNode, which will be used to construct coding work.



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