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From "Kai Zheng (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12041) Implement another Reed-Solomon coder in pure Java
Date Tue, 03 Nov 2015 00:20:27 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12041?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14986355#comment-14986355

Kai Zheng commented on HADOOP-12041:

Looks like it isn't too bad for the large portion of new codes :). Will refine and update
the patch today.

> Implement another Reed-Solomon coder in pure Java
> -------------------------------------------------
>                 Key: HADOOP-12041
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12041
>             Project: Hadoop Common
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Kai Zheng
>         Attachments: HADOOP-12041-v1.patch, HADOOP-12041-v2.patch
> Currently existing Java RS coders based on {{GaloisField}} implementation have some drawbacks
or limitations:
> * The decoder computes not really erased units unnecessarily (HADOOP-11871);
> * The decoder requires parity units + data units order for the inputs in the decode API
> * Need to support or align with native erasure coders regarding concrete coding algorithms
and matrix, so Java coders and native coders can be easily swapped in/out and transparent
to HDFS (HADOOP-12010);
> * It's unnecessarily flexible but incurs some overhead, as HDFS erasure coding is totally
a byte based data system, we don't need to consider other symbol size instead of 256.
> This desires to implement another  RS coder in pure Java, in addition to the existing
{{GaliosField}} from HDFS-RAID. The new Java RS coder will be favored and used by default
to resolve the related issues. The old HDFS-RAID originated coder will still be there for
comparing, and converting old data from HDFS-RAID systems.

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