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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2017) A partial rollback cause the new changes done after upgrade to be visible after rollback
Date Thu, 02 Jun 2011 16:58:47 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2017?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13042876#comment-13042876

Todd Lipcon commented on HDFS-2017:

Can you please answer the questions I asked on the list the other day?

>Steps to reproduce :
>  1) Configure n>1 ,say 3 name dirs
>  2) Upgrade Namenode - After upgrade is over for 1st dir , stop/kill the namenode

Are you running the "upgrade" command with 0.21?
>  3) Start namenode and write some files (delta) & then stop

> Which version do you restart with? 0.21 again or 0.20?
  4) Rollback namenode

> Which version do you run the rollback command with?

> A partial rollback cause the new changes done after upgrade to be visible after rollback
> ----------------------------------------------------------------------------------------
>                 Key: HDFS-2017
>                 URL: https://issues.apache.org/jira/browse/HDFS-2017
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 0.20.1
>            Reporter: HariSree
>            Priority: Minor
>              Labels: rollback, upgrade
> This is the scenario :
> Namenode has 3 name dirs configured ..
> 1) Namenode upgrade starts - Upgrade fails after 1st directory is upgraded (2nd and 3rd
dir is left unchanged ..) { like , Namenode process down }
> 2) Namenode starts and new files written .. 
> 3) Namenode shutdown and rollbacked
> Since Namenode is saving the latest image dir(the upgraded 1st dir since checkpointtime
is incremented during upgrade for this dir) will be loaded and saved to all dirs during loadfsimage
> But if a ROLLBACK is done , the 1st dir will be rolled back (the older copy becomes current
and its checkpointtime is now LESS than other dirs ..) and others left behind since they dont
contain previous .. Now during loadfsimage , the 2nd dir will be selected since it has the
highest checkpoint time and saved to all dirs (including 1st ) .. Now due to this , the new
changes b/w UPGRADE and ROLLBACK present in 2nd dir gets reflected even after ROLLBACK ..
> This is not the case with a SUCCESSFUL Upgrade/Rollback (New changes lost after rollback)..

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