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From "sam rash (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-1218) 20 append: Blocks recovered on startup should be treated with lower priority during block synchronization
Date Tue, 22 Jun 2010 00:54:05 GMT

    [ https://issues.apache.org/jira/browse/HDFS-1218?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12880987#action_12880987
] 

sam rash commented on HDFS-1218:
--------------------------------

a few questions

1. this assumes a DN goes down with the client (either in tandem, or on the same box) and
that the NN initiates lease recovery later correct?

2. the idea here is that RBW should have lengths longer than RWR, but both will have the same
genstamp?
 
If so, why aren't we just taking the replica with the longest length? Is there a reason to


3.  if sync() did not complete, there is no violation.  do I follow?  i agree we can try to
recover more data if it's there, but i just want to make sure i'm on the same page



> 20 append: Blocks recovered on startup should be treated with lower priority during block
synchronization
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: HDFS-1218
>                 URL: https://issues.apache.org/jira/browse/HDFS-1218
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: data-node
>    Affects Versions: 0.20-append
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: 0.20-append
>
>         Attachments: hdfs-1281.txt
>
>
> When a datanode experiences power loss, it can come back up with truncated replicas (due
to local FS journal replay). Those replicas should not be allowed to truncate the block during
block synchronization if there are other replicas from DNs that have _not_ restarted.

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