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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-744) Support hsync in HDFS
Date Tue, 25 Sep 2012 15:17:09 GMT

    [ https://issues.apache.org/jira/browse/HDFS-744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13462855#comment-13462855
] 

Lars Hofhansl commented on HDFS-744:
------------------------------------

You are right Luke. I implemented this in the context of hadoop-2 (i.e. with HDFS-265).
It seems to get this right HDFS-265 needs to be revisited again.

Will look at your suggestion (doing sync in the data thread). As long as the syncs (or flushes)
are not serialized it's fine (otherwise nobody is going to switch this on).

                
> Support hsync in HDFS
> ---------------------
>
>                 Key: HDFS-744
>                 URL: https://issues.apache.org/jira/browse/HDFS-744
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: data-node, hdfs client
>            Reporter: Hairong Kuang
>            Assignee: Lars Hofhansl
>             Fix For: 2.0.2-alpha
>
>         Attachments: HDFS-744-2.0-v1.patch, HDFS-744-2.0-v2.patch, HDFS-744-trunk.patch,
HDFS-744-trunk-v2.patch, HDFS-744-trunk-v3.patch, HDFS-744-trunk-v4.patch, HDFS-744-trunk-v5.patch,
HDFS-744-trunk-v6.patch, HDFS-744-trunk-v7.patch, HDFS-744-trunk-v8.patch, hdfs-744.txt, hdfs-744-v2.txt,
hdfs-744-v3.txt
>
>
> HDFS-731 implements hsync by default as hflush. As descriibed in HADOOP-6313, the real
expected semantics should be "flushes out to all replicas and all replicas have done posix
fsync equivalent - ie the OS has flushed it to the disk device (but the disk may have it in
its cache)." This jira aims to implement the expected behaviour.

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