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From "Todd Lipcon (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-2794) HA: Active NN may purge edit log files before standby NN has a chance to read them
Date Mon, 16 Jan 2012 07:07:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-2794?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13186739#comment-13186739
] 

Todd Lipcon commented on HDFS-2794:
-----------------------------------

Worth noting that this only happens if the admin explicitly invokes saveNamespace on the active
node more times than the configured retention count (or restarts serveral times without running
the SBN in between). So it's easy to work-around by configuring the retention count high,
and in the scenario that you do hit the problem, you can simply scp any image from the active
and restart the SBN.
                
> HA: Active NN may purge edit log files before standby NN has a chance to read them
> ----------------------------------------------------------------------------------
>
>                 Key: HDFS-2794
>                 URL: https://issues.apache.org/jira/browse/HDFS-2794
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: ha, name-node
>    Affects Versions: HA branch (HDFS-1623)
>            Reporter: Aaron T. Myers
>            Assignee: Aaron T. Myers
>
> Given that the active NN is solely responsible for purging finalized edit log segments,
and given that the active NN has no way of knowing when the standby reads edit logs, it's
 possible that the standby NN could fail to read all edits it needs before the active purges
the files.

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