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From "Sanjay Radia (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2026) 1073: 2NN needs to handle case of reformatted NN better
Date Fri, 03 Jun 2011 20:56:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13044042#comment-13044042
] 

Sanjay Radia commented on HDFS-2026:
------------------------------------

On a related note, each edits should have the same info in its header so that we don't accidentally
use mismatching edits and images.  This can occur if our future checkpoint service simply
copies the new image to the dir.

> 1073: 2NN needs to handle case of reformatted NN better
> -------------------------------------------------------
>
>                 Key: HDFS-2026
>                 URL: https://issues.apache.org/jira/browse/HDFS-2026
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: name-node
>    Affects Versions: Edit log branch (HDFS-1073)
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Critical
>             Fix For: Edit log branch (HDFS-1073)
>
>
> Currently in the 1073 branch, the following steps ends up with a very confused 2NN:
> - format NN, run NN
> - start 2NN, perform some checkpoints
> - reformat NN, start NN on new namespace
> - restart same 2NN
> The 2NN currently saves the new VERSION info into its local storage directory but doesn't
clear out the old checkpoint or edits files. This is obviously wrong and might lead to a corrupt
checkpoint getting uploaded. 
> If the 2NN has storage directories with VERSION info, and connects to an NN with different
VERSION info, there are two alternatives:
> a) refuse to perform any checkpoints until the operator issues a "secondarynamenode -format"
command (this is similar to how the backupnode/checkpointnode works)
> b) clear the current contents of the storage directory and save the new NN's VERSION
info.

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