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From "Kai Sasaki (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (HDFS-9965) CLONE - Representing striped block groups in NameNode with hierarchical naming protocol
Date Tue, 15 Mar 2016 08:47:33 GMT

     [ https://issues.apache.org/jira/browse/HDFS-9965?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Kai Sasaki resolved HDFS-9965.
------------------------------
    Resolution: Invalid

> CLONE - Representing striped block groups in NameNode with hierarchical naming protocol
> ---------------------------------------------------------------------------------------
>
>                 Key: HDFS-9965
>                 URL: https://issues.apache.org/jira/browse/HDFS-9965
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: dragon
>            Assignee: Zhe Zhang
>             Fix For: 3.0.0
>
>
> All erasure codec operations center around the concept of _block group_; they are formed
in initial encoding and looked up in recoveries and conversions. A lightweight class {{BlockGroup}}
is created to record the original and parity blocks in a coding group, as well as a pointer
to the codec schema (pluggable codec schemas will be supported in HDFS-7337). With the striping
layout, the HDFS client needs to operate on all blocks in a {{BlockGroup}} concurrently. Therefore
we propose to extend a file’s inode to switch between _contiguous_ and _striping_ modes,
with the current mode recorded in a binary flag. An array of BlockGroups (or BlockGroup IDs)
is added, which remains empty for “traditional” HDFS files with contiguous block layout.
> The NameNode creates and maintains {{BlockGroup}} instances through the new {{ECManager}}
component; the attached figure has an illustration of the architecture. As a simple example,
when a {_Striping+EC_} file is created and written to, it will serve requests from the client
to allocate new {{BlockGroups}} and store them under the {{INodeFile}}. In the current phase,
{{BlockGroups}} are allocated both in initial online encoding and in the conversion from replication
to EC. {{ECManager}} also facilitates the lookup of {{BlockGroup}} information for block recovery
work.



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