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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 in INodeFile and eliminate notion of EC zones
Date Fri, 31 Jul 2015 18:02:06 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14649566#comment-14649566
] 

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

{code}
... Under the scope of this JIRA, the file's EC policy won't be changed. If it was created
under EC zone A it will carry EC policy A with it when being moved. Could you explain a bit
more why "If yes, we could eliminate EC zones. Otherwise, we should keep EC zone."?
{code}
This is semantic different from StoragePolicy.  We should use the same semantic as StoragePolicy.
 Let's keep EC zone for the moment.

{code}
As a follow-on we could enable an "inherit" mode similar as StoragePolicy.
{code}
No, we cannot change semantic over time.

> Erasure coding: store EC schema and cell size in INodeFile and eliminate notion of 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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