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Date: Tue, 28 May 2013 17:33:21 +0000 (UTC)
From: "Todd Lipcon (JIRA)" <jira@apache.org>
To: hdfs-dev@hadoop.apache.org
Message-ID: <JIRA.12615845.1352775185495.30352.1369762401390@arcas>
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Subject: [jira] [Resolved] (HDFS-4184) Add the ability for Client to provide
 more hint information for DataNode to manage the OS buffer cache more
 accurate
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     [ https://issues.apache.org/jira/browse/HDFS-4184?page=3Dcom.atlassian=
.jira.plugin.system.issuetabpanels:all-tabpanel ]

Todd Lipcon resolved HDFS-4184.
-------------------------------

    Resolution: Duplicate
   =20
> Add the ability for Client to provide more hint information for DataNode =
to manage the OS buffer cache more accurate
> -------------------------------------------------------------------------=
-------------------------------------------
>
>                 Key: HDFS-4184
>                 URL: https://issues.apache.org/jira/browse/HDFS-4184
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: binlijin
>
> HDFS now has the ability to use posix_fadvise and sync_data_range syscall=
s to manage the OS buffer cache.
> {code}
> When hbase read hlog the data we can set dfs.datanode.drop.cache.behind.r=
eads to true to drop data out of the buffer cache when performing sequentia=
l reads.
> When hbase write hlog we can set dfs.datanode.drop.cache.behind.writes to=
 true to drop data out of the buffer cache after writing
> When hbase read hfile during compaction we can set dfs.datanode.readahead=
.bytes to a non-zero value to trigger readahead for sequential reads=EF=BC=
=8C and also set dfs.datanode.drop.cache.behind.reads to true to drop data =
out of the buffer cache when performing sequential reads.
> and so on...=20
> {code}
> Current we can only set these feature global in datanode=EF=BC=8Cwe shoul=
d set these feature per session.

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