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https://issues.apache.org/jira/browse/HADOOP-2012?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12548824
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Raghu Angadi commented on HADOOP-2012:
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> The question here is whether we would go with our current decision if we new 
> it will not be supported on windows?
A related concern is whether this is required for appends anyway.

> Periodic verification at the Datanode
> -------------------------------------
>
>                 Key: HADOOP-2012
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2012
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Raghu Angadi
>            Assignee: Raghu Angadi
>             Fix For: 0.16.0
>
>         Attachments: HADOOP-2012.patch, HADOOP-2012.patch, HADOOP-2012.patch, 
> HADOOP-2012.patch
>
>
> Currently on-disk data corruption on data blocks is detected only when it is 
> read by the client or by another datanode.  These errors are detected much 
> earlier if datanode can periodically verify the data checksums for the local 
> blocks.
> Some of the issues to consider :
> - How should we check the blocks ( no more often than once every couple of 
> weeks ?)
> - How do we keep track of when a block was last verfied ( there is a .meta 
> file associcated with each lock ).
> - What action to take once a corruption is detected
> - Scanning should be done as a very low priority with rest of the datanode 
> disk traffic in mind.

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