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From "Tsz Wo Nicholas Sze (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8833) Erasure coding: store EC schema and cell size with INodeFile and eliminate EC zones
Date Thu, 30 Jul 2015 18:29:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14648084#comment-14648084
] 

Tsz Wo Nicholas Sze commented on HDFS-8833:
-------------------------------------------

What is the semantic of moving a file under EC zone A to EC zone B?  Would the file be changed
from EC scheme A to EC schema B?  If yes, we could eliminate EC zones.  Otherwise, we should
keep EC zone.

> Erasure coding: store EC schema and cell size with INodeFile and eliminate EC zones
> -----------------------------------------------------------------------------------
>
>                 Key: HDFS-8833
>                 URL: https://issues.apache.org/jira/browse/HDFS-8833
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>    Affects Versions: HDFS-7285
>            Reporter: Zhe Zhang
>            Assignee: Zhe Zhang
>
> We have [discussed | https://issues.apache.org/jira/browse/HDFS-7285?focusedCommentId=14357754&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14357754]
storing EC schema with files instead of EC zones and recently revisited the discussion under
HDFS-8059.
> As a recap, the _zone_ concept has severe limitations including renaming and nested configuration.
Those limitations are valid in encryption for security reasons and it doesn't make sense to
carry them over in EC.
> This JIRA aims to store EC schema and cell size on {{INodeFile}} level. For simplicity,
we should first implement it as an xattr and consider memory optimizations (such as moving
it to file header) as a follow-on. We should also disable changing EC policy on a non-empty
file / dir in the first phase.



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