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https://issues.apache.org/jira/browse/HDFS-3540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13448673#comment-13448673
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Tsz Wo (Nicholas), SZE commented on HDFS-3540:
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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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