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Date: Fri, 19 Oct 2007 15:18:50 -0700 (PDT)
From: "Raghu Angadi (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Updated: (HADOOP-2012) Periodic verification at the Datanode
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     [ https://issues.apache.org/jira/browse/HADOOP-2012?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Raghu Angadi updated HADOOP-2012:
---------------------------------

    Attachment: HADOOP-2012.patch

Updated the patch. SCAN_PERIOD was set to negative value by mistake.

> 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
>         Attachments: 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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