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https://issues.apache.org/jira/browse/HDFS-3540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13448934#comment-13448934
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Colin Patrick McCabe commented on HDFS-3540:
--------------------------------------------
bq. The main issue of branch-1 recovery mode is silent data loss.
Recovery Mode prompts the sysadmin before doing anything. Edit Log Toleration
never prompts.
Recovery Mode can't be turned on in the configuration. Edit Log Toleration can
only be turned on in the configuration.
It is Edit Log Toleration that can lead to silent data loss. Recovery Mode
never does.
bq. 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.
If we need to add more functionality, then let's add more functionality, not
remove it.
> 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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