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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1704) Throttling for HDFS Trash purging
Date Thu, 06 Sep 2007 17:56:32 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1704?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12525484
] 

Raghu Angadi commented on HADOOP-1704:
--------------------------------------

> Raghu's block crc upgrade code throttles the deletion of .crc files.

blockCrc upgrade does not throttle deletes explicitly. It deletes in a single thread and each
deletiion results in editsLog entry.. these two naturally throttle the rate to around 700-800
deletes a second. Deleting a directory deletes whole tree with sigle editsLog entry. This
is the difference. 

The similarity is that that none of these 5M blocks were removed from the namespace until
after the upgrade is complete. In that sense memory overhead is same as deleting 5M files
in one shot.

> Throttling for HDFS Trash purging
> ---------------------------------
>
>                 Key: HADOOP-1704
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1704
>             Project: Hadoop
>          Issue Type: Bug
>          Components: dfs
>            Reporter: dhruba borthakur
>
> When HDFS Trash is enabled, deletion of a file/directory results in it being moved to
the "Trash" directory. The "Trash" directory is periodically purged by the Namenode. This
means that all files/directories that users deleted in the last Trash period, gets "really"
deleted when the Trash purging occurs. This might cause a burst of file/directory deletions.
> The Namenode tracks blocks that belonged to deleted files in a data structure named "RecentInvalidateSets".
There is a possibility that Trash purging may cause this data structure to bloat, causing
undesireable behaviour of the Namenode.

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