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From "Andrew Wang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7337) Configurable and pluggable Erasure Codec and schema
Date Tue, 21 Mar 2017 21:27:41 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15935364#comment-15935364
] 

Andrew Wang commented on HDFS-7337:
-----------------------------------

Thanks for reviving this [~drankye]!

Will we allow users to define new EC codecs? If so, we could exercise it by refactoring out
rs-legacy to be a pluggable policy as a test, or HDFS-9345 to implement a dummy codec. It
looks like the ECSchemaProto and ErasureCodingPolicyProto support this kind of pluggability
already, so we can transmit this info to the client.

I think it'd be good to keep this info in the normal NN metadata if possible. Without the
policy information, you essentially have data loss, and from an operational POV, admins might
not be used to backing up an extra XML file.

> Configurable and pluggable Erasure Codec and schema
> ---------------------------------------------------
>
>                 Key: HDFS-7337
>                 URL: https://issues.apache.org/jira/browse/HDFS-7337
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: erasure-coding
>            Reporter: Zhe Zhang
>            Assignee: Kai Zheng
>              Labels: hdfs-ec-3.0-nice-to-have
>         Attachments: HDFS-7337-prototype-v1.patch, HDFS-7337-prototype-v2.zip, HDFS-7337-prototype-v3.zip,
PluggableErasureCodec.pdf, PluggableErasureCodec-v2.pdf, PluggableErasureCodec-v3.pdf
>
>
> According to HDFS-7285 and the design, this considers to support multiple Erasure Codecs
via pluggable approach. It allows to define and configure multiple codec schemas with different
coding algorithms and parameters. The resultant codec schemas can be utilized and specified
via command tool for different file folders. While design and implement such pluggable framework,
it’s also to implement a concrete codec by default (Reed Solomon) to prove the framework
is useful and workable. Separate JIRA could be opened for the RS codec implementation.
> Note HDFS-7353 will focus on the very low level codec API and implementation to make
concrete vendor libraries transparent to the upper layer. This JIRA focuses on high level
stuffs that interact with configuration, schema and etc.



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