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https://issues.apache.org/jira/browse/HADOOP-2012?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12548756
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eric baldeschwieler commented on HADOOP-2012:
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I'd really rather see us get this right for supported platforms rather than 
declare an issue done when we know it does not work on some platforms.

This is particularly vexing when design choices could clearly be made that 
would avoid these issues.

-1

> 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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