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From "eric baldeschwieler (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2012) Periodic verification at the Datanode
Date Tue, 30 Oct 2007 06:55:50 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2012?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12538683
] 

eric baldeschwieler commented on HADOOP-2012:
---------------------------------------------

what value is there in scanning a single block continuously in the extreme case?

Seems like we should do our part to keep our carbon footprint down.

> 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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