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https://issues.apache.org/jira/browse/HDFS-1143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12993260#comment-12993260
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Suresh Srinivas commented on HDFS-1143:
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Blocks collected from the detached inode are deleted without FSNamesystem
block. Currently the block map in BlockManager and DatanodeDescriptor BlockInfo
link list is only protected by FSNamesystem lock. What is the synchronization
for them when delete blocks. That is the reason why HDFS-173 decided to delete
blocks holding FSNamesystem lock for a short duration at a time.
> Implement Background deletion
> -----------------------------
>
> Key: HDFS-1143
> URL: https://issues.apache.org/jira/browse/HDFS-1143
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: name-node
> Affects Versions: 0.22.0
> Reporter: Dmytro Molkov
> Assignee: Scott Chen
> Attachments: HDFS-1143-v2.txt, HDFS-1143.txt
>
>
> Right now if you try to delete massive number of files from the namenode it
> will freeze (sometimes for minutes). Most of the time is spent going through
> the blocks map and invalidating all the blocks.
> This can probably be improved by having a background GC process. The deletion
> will basically just remove the inode being deleted and then give the subtree
> that was just deleted to the background thread running cleanup.
> This way the namenode becomes available for the clients soon after deletion,
> and all the heavy operations are done in the background.
> Thoughts?
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