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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7866) Erasure coding: NameNode manages multiple erasure coding policies
Date Wed, 02 Mar 2016 06:25:18 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7866?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15175122#comment-15175122
] 

Zhe Zhang commented on HDFS-7866:
---------------------------------

Sorry for the confusion Rui. I meant some text-base illustration like below. I think it will
be useful to illustrate the header format for both contiguous and striped blocks. If it's
still confusing, feel free to skip it and I'll be happy to do it as a follow-on.
{code}
// StripedBlockUtil
 *  | <----  Block Group ----> |   <- Block Group: logical unit composing
 *  |                          |        striped HDFS files.
 *  blk_0      blk_1       blk_2   <- Internal Blocks: each internal block
 *    |          |           |          represents a physically stored local
 *    v          v           v          block file
 * +------+   +------+   +------+
 * |cell_0|   |cell_1|   |cell_2|  <- {@link StripingCell} represents the
 * +------+   +------+   +------+       logical order that a Block Group should
 * |cell_3|   |cell_4|   |cell_5|       be accessed: cell_0, cell_1, ...
 * +------+   +------+   +------+
 * |cell_6|   |cell_7|   |cell_8|
 * +------+   +------+   +------+
 * |cell_9|
 * +------+  <- A cell contains cellSize bytes of data
{code}

> Erasure coding: NameNode manages multiple erasure coding policies
> -----------------------------------------------------------------
>
>                 Key: HDFS-7866
>                 URL: https://issues.apache.org/jira/browse/HDFS-7866
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Rui Li
>         Attachments: HDFS-7866-v1.patch, HDFS-7866-v2.patch, HDFS-7866-v3.patch, HDFS-7866.10.patch,
HDFS-7866.4.patch, HDFS-7866.5.patch, HDFS-7866.6.patch, HDFS-7866.7.patch, HDFS-7866.8.patch,
HDFS-7866.9.patch
>
>
> This is to extend NameNode to load, list and sync predefine EC schemas in authorized
and controlled approach. The provided facilities will be used to implement DFSAdmin commands
so admin can list available EC schemas, then could choose some of them for target EC zones.



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