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From "Jing Zhao (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HDFS-9789) Correctly update DataNode's scheduled block size when writing small EC file
Date Wed, 10 Feb 2016 21:33:18 GMT

     [ https://issues.apache.org/jira/browse/HDFS-9789?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Jing Zhao updated HDFS-9789:
----------------------------
    Status: Patch Available  (was: Open)

> Correctly update DataNode's scheduled block size when writing small EC file
> ---------------------------------------------------------------------------
>
>                 Key: HDFS-9789
>                 URL: https://issues.apache.org/jira/browse/HDFS-9789
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>    Affects Versions: 3.0.0
>            Reporter: Jing Zhao
>            Assignee: Jing Zhao
>         Attachments: HDFS-9789.000.patch
>
>
> Currently DatanodeDescriptor's scheduled block size is increased when allocating a new
block. It is then decreased when NN receives IBR from the DN.
> When writing an erasure-coded file whose size is less a stripe, we can have less than
6 internal data blocks. Then we never decrease the scheduled block size for Datanodes that
are actually not used for storing any internal block. When writing large amount of small EC
files within a short period, this may cause NN to wrongly exclude DN for writing due to high
scheduled block size.



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