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From "Vinayakumar B (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 08:58:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14647360#comment-14647360
] 

Vinayakumar B commented on HDFS-8833:
-------------------------------------

{quote}path: Refer to an empty and already created directory in HDFS. This is a mandatory
parameter.
schemaName: This is an optional parameter, specified using ā€˜-sā€™ flag. Refer to the name
of ECSchema to be used for erasure coding of direct children (files or subdirectories) of
this directory. If not specified the system default ECSchema will be used.{quote}
Here, description for path and schemaName should be updated. It could be file also. And need
not be empty. I think can change after creating files also, only thing is further files will
inherit different ECPolicy.


> 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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