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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-3540) Further improvement on recovery mode and edit log toleration in branch-1
Date Wed, 05 Sep 2012 12:37:09 GMT

    [ https://issues.apache.org/jira/browse/HDFS-3540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13448673#comment-13448673
] 

Tsz Wo (Nicholas), SZE commented on HDFS-3540:
----------------------------------------------

First of all, let's focus the discussion in branch-1 since edit log recovery mode feature
in branch-1 and >= branch-2 are quite different.

The main issue of branch-1 recovery mode is silent data loss.  A minor issue is that it does
not provide useful features: it only let admin to choose "stop reading" or "quit without saving".
 "Stop reading" can be done by setting toleration length and "quit without saving" simply
means that NN cannot start up.

For edit log toleration, admin could first set toleration length to zero.  If corruption is
found, the admin could change the toleration length accordingly.

                
> Further improvement on recovery mode and edit log toleration in branch-1
> ------------------------------------------------------------------------
>
>                 Key: HDFS-3540
>                 URL: https://issues.apache.org/jira/browse/HDFS-3540
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: name-node
>    Affects Versions: 1.2.0
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>
> *Recovery Mode*: HDFS-3479 backported HDFS-3335 to branch-1.  However, the recovery mode
feature in branch-1 is dramatically different from the recovery mode in trunk since the edit
log implementations in these two branch are different.  For example, there is UNCHECKED_REGION_LENGTH
in branch-1 but not in trunk.
> *Edit Log Toleration*: HDFS-3521 added this feature to branch-1 to remedy UNCHECKED_REGION_LENGTH
and to tolerate edit log corruption.
> There are overlaps between these two features.  We study potential further improvement
in this issue.

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