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From "Kai Zheng (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-8074) Define a system-wide default EC schema
Date Wed, 08 Apr 2015 09:06:13 GMT

    [ https://issues.apache.org/jira/browse/HDFS-8074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14484971#comment-14484971

Kai Zheng commented on HDFS-8074:

Thanks [~umamaheswararao] and [~vinayrpet] for the thoughts here.

Vinay, I'm thinking if we have the system default schema defined in the XML file, it may be
not so reliable as you meant, saying never changed after installation. It's because the XML
file is for admin to define (additional) schemas for a deployment. The system default schema
should be definitely reliable there as the fallback by default. I agree we may need to configure
the values, but might be not in the XML file? How about just having the key parameters configured
in core-site.xml? Thinking about that it must use the fixed RS codec, we only need 2 properties
for the purpose.

bq.why cant make schema parameter mandatory for ec zone at the time of creation.? instead
of having system default schema
Sure you're right. We should change ECZone constructor as you said, making it mandatory. We
need to revisit the aspect, like adding the schema parameter to create an EC zone. Having
the system default schema isn't for the purpose, it's useful some admin just wants to have
a global one and then use it by default in most cases. Make sense?

> Define a system-wide default EC schema
> --------------------------------------
>                 Key: HDFS-8074
>                 URL: https://issues.apache.org/jira/browse/HDFS-8074
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Kai Zheng
>         Attachments: HDFS-8074-v1.patch, HDFS-8074-v2.patch, HDFS-8074-v3.patch
> It's good to have a system default EC schema first with fixed values before we support
more schemas. This makes sense to resolve some dependencies before HDFS-7866 can be done in
whole. The default system schema is also needed anyhow essentially when admin just wants to
use it.

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