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https://issues.apache.org/jira/browse/HDFS-1104?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12860341#action_12860341
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Jakob Homan commented on HDFS-1104:
-----------------------------------
Would #4 fix the issue we saw completely, while keeping the previously defined
behavior that most people seem to like? It seems that this edge case we've
encountered reveals a deficiency in how we're flushing edits, not in fsck
itself.
> Fsck triggers full GC on NameNode
> ---------------------------------
>
> Key: HDFS-1104
> URL: https://issues.apache.org/jira/browse/HDFS-1104
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: name-node
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Priority: Blocker
> Fix For: 0.20.3, 0.21.0, 0.22.0
>
>
> A NameNode at one of our clusters fell into full GC while fsck was performed.
> Digging into the problem shows that it is caused by how NameNode handles the
> access time of a file.
> Fsck calls open on every file in the checked directory to get the file's
> block locations. Each open changes the file's access time and then leads to
> writing a transaction entry to the edit log. The current code optimizes open
> so that it returns without issuing synchronizing the edit log to the disk. It
> happened that in our cluster no other jobs were running while fsck was
> performed. No edit log sync was ever called. So all open transactions were
> kept in memory. When the edit log buffer got full, it automatically doubled
> its space by allocating a new buffer. Full GC happened when no contiguous
> space were found when allocating a new bigger buffer.
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