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https://issues.apache.org/jira/browse/HDFS-3540?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13447906#comment-13447906
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Colin Patrick McCabe commented on HDFS-3540:
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bq. Correct me if I am wrong: Recovery Mode without HDFS-3479 means the entire
end-of-log is not checked and, therefore, the silent data loss length is not
limited. It is even worst.
No, that is incorrect.
Recovery mode has always read up to the end of the log, and it always will.
The confusion arises because sometimes we are not very good at determining
where the "end of the log" is.
I filed and implemented HDFS-3479 because I noticed that in certain scenarios
we would decide that the edit log ended before it really did because we spotted
an {{OP_INVALID}}.
The unchecked region which we've been discussing only applied to HDFS-3479
corruption, not to any other type of corruption. Frankly, the unchecked region
was a mistake.
However, none of this has *anything* to do with recovery mode. HDFS-3004 and
HDFS-3479 were separate JIRAs, that implemented separate features.
> 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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