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From "Walter Su (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7661) Erasure coding: support hflush and hsync
Date Wed, 06 Jan 2016 08:33:40 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7661?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15085202#comment-15085202
] 

Walter Su commented on HDFS-7661:
---------------------------------

You totally miss my point.
A successful flush is a guarantee that the data is safe.
If 1st flush succeed, data written before 1st flush is safe.
If 2nd flush failed, data written between 1st ~ 2nd flush is lost. User can restart writing
at 1st flush point (with a lease recovery).

According to the description, if the data before 1st flush is damaged, how can we restart
at 1st flush point? Client have to restart at the beginning of current block. Then what's
the meaning of "flush"?

> Erasure coding: support hflush and hsync
> ----------------------------------------
>
>                 Key: HDFS-7661
>                 URL: https://issues.apache.org/jira/browse/HDFS-7661
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>            Reporter: Tsz Wo Nicholas Sze
>            Assignee: GAO Rui
>         Attachments: EC-file-flush-and-sync-steps-plan-2015-12-01.png, HDFS-7661-unitTest-wip-trunk.patch,
HDFS-EC-file-flush-sync-design-version1.1.pdf
>
>
> We also need to support hflush/hsync and visible length. 



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