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Date: Mon, 7 Nov 2016 05:30:58 +0000 (UTC)
From: "Kai Zheng (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.13011232.1476155872000.205996.1478496658527@Atlassian.JIRA>
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References: <JIRA.13011232.1476155872000@Atlassian.JIRA> <JIRA.13011232.1476155872251@arcas>
Subject: [jira] [Commented] (HDFS-10994) Support an XOR policy XOR-2-1-64k
 in HDFS
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archived-at: Mon, 07 Nov 2016 05:31:00 -0000


    [ https://issues.apache.org/jira/browse/HDFS-10994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15643174#comment-15643174 ] 

Kai Zheng commented on HDFS-10994:
----------------------------------

Not relevant to the work here, but just raising some questions by the way, looking at the following codes:
{code}
   public static final byte RS_6_3_POLICY_ID = 0;
   public static final byte RS_3_2_POLICY_ID = 1;
   public static final byte RS_6_3_LEGACY_POLICY_ID = 2;
+  public static final byte XOR_2_1_POLICY_ID = 3;
{code}

* Suggest we start the {{POLICY_ID}} from 1 instead of 0, to avoid some unexpected errors in codes since 0 is default value for integer variables. I had discussed offline with [~Sammi] about this and the idea sounds good so far.

* Maybe we can remove related {{LEGACY_POLICY_ID}} as [~andrew.wang] commented elsewhere we don't need to use any legacy policies in HDFS side, though I want to keep the legacy coders in Hadoop side.

How would you think? Maybe [~andrew.wang] and [~zhz] could also give some comments? Thanks. If sounds good to do these, separate issue would be good.

> Support an XOR policy XOR-2-1-64k in HDFS
> -----------------------------------------
>
>                 Key: HDFS-10994
>                 URL: https://issues.apache.org/jira/browse/HDFS-10994
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: erasure-coding
>    Affects Versions: 3.0.0-alpha1
>            Reporter: SammiChen
>            Assignee: SammiChen
>              Labels: hdfs-ec-3.0-must-do
>         Attachments: HDFS-10994-v1.patch, HDFS-10994-v2.patch, HDFS-10994-v3.patch
>
>
> So far, "hdfs erasurecode" command supports three policies, RS-DEFAULT-3-2-64k, RS-DEFAULT-6-3-64k and RS-LEGACY-6-3-64k. This task is going to add XOR-2-1-64k policy to this command.


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