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https://issues.apache.org/jira/browse/HADOOP-1869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12556799#action_12556799
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Allen Wittenauer commented on HADOOP-1869:
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Now that we have permissions and ownerships, such an access log would also need 
to differentiate between reads, writes, ownership changes, and permission 
changes.  This would be _extremely_ helpful in case forensics need to be 
performed to track down someone doing Bad Things(tm).

> access times of HDFS files
> --------------------------
>
>                 Key: HADOOP-1869
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1869
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: dhruba borthakur
>
> HDFS should support some type of statistics that allows an administrator to 
> determine when a file was last accessed. 
> Since HDFS does not have quotas yet, it is likely that users keep on 
> accumulating files in their home directories without much regard to the 
> amount of space they are occupying. This causes memory-related problems with 
> the namenode.
> Access times are costly to maintain. AFS does not maintain access times. I 
> thind DCE-DFS does maintain access times with a coarse granularity.
> One proposal for HDFS would be to implement something like an "access bit". 
> 1. This access-bit is set when a file is accessed. If the access bit is 
> already set, then this call does not result in a transaction.
> 2. A FileSystem.clearAccessBits() indicates that the access bits of all files 
> need to be cleared.
> An administrator can effectively use the above mechanism (maybe a daily cron 
> job) to determine files that are recently used.

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