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Date: Wed, 5 Aug 2015 06:33:04 +0000 (UTC)
From: "Vinayakumar B (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12849790.1438125336000.375067.1438756384984@Atlassian.JIRA>
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Subject: [jira] [Commented] (HDFS-8833) Erasure coding: store EC schema and
 cell size in INodeFile and eliminate notion of EC zones
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    [ https://issues.apache.org/jira/browse/HDFS-8833?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14654892#comment-14654892 ] 

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

bq. Remove isStriped from INodeFile header and reduce replication factor to 6 bits.
Instead of reducing the replication to 6 bits, how about reducing {{preferredBlockSize}} to 42 bits? still value upto 2 TB can be stored in 42 bits.

> 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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