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From "Lars Hofhansl (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-744) Support hsync in HDFS
Date Sun, 06 May 2012 06:50:21 GMT

    [ https://issues.apache.org/jira/browse/HDFS-744?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269147#comment-13269147

Lars Hofhansl commented on HDFS-744:

Turns out no new DataTransferProtocol option is needed, the client can send a sync packet
to indicate that the current block needs to be sync'ed even before it is closed.

I'm almost done with a patch that does what I have described above. The only part remaining
is allowing the client to send an empty sync packet if no data is outstanding (currently a
packet with payloadLen==0 indicates EOF).

> Support hsync in HDFS
> ---------------------
>                 Key: HDFS-744
>                 URL: https://issues.apache.org/jira/browse/HDFS-744
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Hairong Kuang
> 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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