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From "Sean Busbey (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (ACCUMULO-884) Take advantage of short circuit read for local files
Date Fri, 18 Apr 2014 20:19:20 GMT

     [ https://issues.apache.org/jira/browse/ACCUMULO-884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Sean Busbey updated ACCUMULO-884:
---------------------------------

    Assignee:     (was: Keith Turner)

For whomever takes this on, take a look at Hadoop 2.2.0 [docs on short circuit local reads|http://hadoop.apache.org/docs/r2.2.0/hadoop-project-dist/hadoop-hdfs/ShortCircuitLocalReads.html]
for the relevant configs.

A nice to have would be some stats on if reads are actually short circuiting, in the TServer
logs or Monitor. I haven't chased down where to get this information, sadly.

> Take advantage of short circuit read for local files
> ----------------------------------------------------
>
>                 Key: ACCUMULO-884
>                 URL: https://issues.apache.org/jira/browse/ACCUMULO-884
>             Project: Accumulo
>          Issue Type: Sub-task
>          Components: docs
>            Reporter: Billie Rinaldi
>
> This is a new feature in hadoop 1.0.x and some versions of 0.22 and 0.23.  It allows
a client to read directly from disk instead of through a DataNode when the data is stored
locally.  Enabling it involves setting two configuration parameters, the first in hdfs-site.xml
and the second in accumulo-site.xml.  We should make sure this works with Accumulo and recommend
it in the documentation.
> - dfs.block.local-path-access.user is the key in datanode configuration to specify the
user allowed to do short circuit read.
> - dfs.client.read.shortcircuit is the key to enable short circuit read at the client
side configuration.
> See HDFS-2246 and http://hbase.apache.org/book/perf.hdfs.configs.html for more information.



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