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https://issues.apache.org/jira/browse/HDFS-9608?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15109068#comment-15109068
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Vinayakumar B commented on HDFS-9608:
-------------------------------------

bq. Inconsistent synchronization of 
org.apache.hadoop.hdfs.server.datanode.fsdataset.AvailableSpaceVolumeChoosingPolicy.balancedPreferencePercent;
 locked 57% of time Unsynchronized access at 
AvailableSpaceVolumeChoosingPolicy.java:57% of time Unsynchronized access at 
AvailableSpaceVolumeChoosingPolicy.java:[line 159]
didnt see that coming. 
IMO, its safe to remove synchronization on getConf() and setConf() in 
AvailableSpaceVolumeChoosingPolicy. as its nowhere else called

> Disk IO imbalance in HDFS with heterogeneous storages
> -----------------------------------------------------
>
>                 Key: HDFS-9608
>                 URL: https://issues.apache.org/jira/browse/HDFS-9608
>             Project: Hadoop HDFS
>          Issue Type: Bug
>    Affects Versions: 2.6.0
>            Reporter: Wei Zhou
>            Assignee: Wei Zhou
>         Attachments: HDFS-9608.01.patch, HDFS-9608.02.patch, 
> HDFS-9608.03.patch, HDFS-9608.04.patch, HDFS-9608.05.patch, HDFS-9608.06.patch
>
>
> Currently RoundRobinVolumeChoosingPolicy use a shared index to choose volumes 
> in HDFS with heterogeneous storages, this leads to non-RR choosing mode for 
> certain type of storage.
> Besides, it uses a shared lock for synchronization which limits the 
> concurrency of volume choosing process. Volume choosing threads that 
> operating on different storage types should be able to run concurrently. 



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