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From "Keith Turner (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ACCUMULO-1946) Include dfs.datanode.synconclose in hdfs configuration documentation
Date Mon, 02 Dec 2013 18:42:41 GMT

    [ https://issues.apache.org/jira/browse/ACCUMULO-1946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13836769#comment-13836769
] 

Keith Turner commented on ACCUMULO-1946:
----------------------------------------

I think encouraging people to set dfs.datanode.synconclose may slow down writes.  [~ecn] did
some experiments with this.   This can be mitigated by increasing tserver.mutation.queue.max,
which will decrease the frequency of wal writes.  Enabling dfs.datanode.synconclose adds a
fixed cost to each write.      I am thinking we should add something to the readme or up that
default a bit.  Its a per writer buffer, so it can not be too big.

> Include dfs.datanode.synconclose in hdfs configuration documentation
> --------------------------------------------------------------------
>
>                 Key: ACCUMULO-1946
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-1946
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: docs
>            Reporter: Josh Elser
>            Assignee: Josh Elser
>             Fix For: 1.5.1, 1.6.0
>
>
> We should be including some writeup about dfs.datanode.synconclose in our documentation
surrounding the HDFS configuration as it better ensures that data is lost in the face of hard
shutdown (power loss) of the datanode process.



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