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https://issues.apache.org/jira/browse/HDFS-3828?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Arun C Murthy updated HDFS-3828:
--------------------------------

    Fix Version/s:     (was: 2.3.0)
                   2.4.0

> Block Scanner rescans blocks too frequently
> -------------------------------------------
>
>                 Key: HDFS-3828
>                 URL: https://issues.apache.org/jira/browse/HDFS-3828
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 0.23.0
>            Reporter: Andy Isaacson
>            Assignee: Andy Isaacson
>             Fix For: 2.4.0
>
>         Attachments: hdfs-3828-1.txt, hdfs-3828-2.txt, hdfs-3828-3.txt, 
> hdfs3828.txt
>
>
> {{BlockPoolSliceScanner#scan}} calls cleanUp every time it's invoked from 
> {{DataBlockScanner#run}} via {{scanBlockPoolSlice}}.  But cleanUp 
> unconditionally roll()s the verificationLogs, so after two iterations we have 
> lost the first iteration of block verification times.  As a result a cluster 
> with just one block repeatedly rescans it every 10 seconds:
> {noformat}
> 2012-08-16 15:59:57,884 INFO  datanode.BlockPoolSliceScanner 
> (BlockPoolSliceScanner.java:verifyBlock(391)) - Verification succeeded for 
> BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> 2012-08-16 16:00:07,904 INFO  datanode.BlockPoolSliceScanner 
> (BlockPoolSliceScanner.java:verifyBlock(391)) - Verification succeeded for 
> BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> 2012-08-16 16:00:17,925 INFO  datanode.BlockPoolSliceScanner 
> (BlockPoolSliceScanner.java:verifyBlock(391)) - Verification succeeded for 
> BP-2101131164-172.29.122.91-1337906886255:blk_7919273167187535506_4915
> {noformat}
> {quote}
> To fix this, we need to avoid roll()ing the logs multiple times per period.



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