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https://issues.apache.org/jira/browse/HDFS-1539?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13697735#comment-13697735
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Dave Latham commented on HDFS-1539:
-----------------------------------

Does anyone have any performance numbers for enabling this?  Or, does anyone 
just have some experience running this on significant workloads in production?  
(Especially HBase?)
                
> prevent data loss when a cluster suffers a power loss
> -----------------------------------------------------
>
>                 Key: HDFS-1539
>                 URL: https://issues.apache.org/jira/browse/HDFS-1539
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: datanode, hdfs-client, namenode
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>             Fix For: 0.23.0, 1.1.1
>
>         Attachments: syncOnClose1.txt, syncOnClose2_b-1.txt, syncOnClose2.txt
>
>
> we have seen an instance where a external outage caused many datanodes to 
> reboot at around the same time.  This resulted in many corrupted blocks. 
> These were recently written blocks; the current implementation of HDFS 
> Datanodes do not sync the data of a block file when the block is closed.
> 1. Have a cluster-wide config setting that causes the datanode to sync a 
> block file when a block is finalized.
> 2. Introduce a new parameter to the FileSystem.create() to trigger the new 
> behaviour, i.e. cause the datanode to sync a block-file when it is finalized.
> 3. Implement the FSDataOutputStream.hsync() to cause all data written to the 
> specified file to be written to stable storage.

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