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https://issues.apache.org/jira/browse/HDFS-9560?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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BELUGA BEHR updated HDFS-9560:
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Attachment: AvailableSpaceVolumeChoosingPolicy.java
> Fair AvailableSpaceVolumeChoosingPolicy
> ---------------------------------------
>
> Key: HDFS-9560
> URL: https://issues.apache.org/jira/browse/HDFS-9560
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: BELUGA BEHR
> Priority: Minor
> Attachments: AvailableSpaceVolumeChoosingPolicy.java
>
>
> I took a look at AvailableSpaceVolumeChoosingPolicy. It seems a bit overkill
> and includes some configuration items that seem a bit arbitrary with no real
> clear guidance on how to effectively use them:
> _dfs.datanode.available-space-volume-choosing-policy.balanced-space-preference-fraction_
> _dfs.datanode.available-space-volume-choosing-policy.balanced-space-threshold_
> I have created an alternative implementation that does not require any
> external configuration, is thread-safe, and requires no synchronization.
> "Weighted Randomized Ordering"
> http://stackoverflow.com/questions/23971365/weighted-randomized-ordering
> Conceptually, a dart-board is constructed of several wedges, each wedge
> represents a disk volume. The more available space that a volume has
> relative to the other volumes, the larger its wedge. Then, a dart is thrown
> at the board and whichever wedge(volume) the dart lands on, that wedge is
> assigned the incoming block.
> Over time, the wedges balance and all have an equal chance of being "hit."
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