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From "Jim Kellerman (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-4379) In HDFS, sync() not yet guarantees data available to the new readers
Date Mon, 19 Jan 2009 22:32:59 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-4379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12665257#action_12665257
] 

Jim Kellerman commented on HADOOP-4379:
---------------------------------------

HBase really needs visibility to partial blocks and restarting HDFS is not an option for a
100+ node cluster.

We don't sync after every record, but sync after a configurable number of writes or after
a configurable amount of time has passed and 
there is unsync'd data.

This really needs to be addressed in 0.19.1, 0.20.1 and trunk.

> In HDFS, sync() not yet guarantees data available to the new readers
> --------------------------------------------------------------------
>
>                 Key: HADOOP-4379
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4379
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: dhruba borthakur
>             Fix For: 0.19.1
>
>         Attachments: 4379_20081010TC3.java, fsyncConcurrentReaders.txt
>
>
> In the append design doc (https://issues.apache.org/jira/secure/attachment/12370562/Appends.doc),
it says
> * A reader is guaranteed to be able to read data that was 'flushed' before the reader
opened the file
> However, this feature is not yet implemented.  Note that the operation 'flushed' is now
called "sync".

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