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https://issues.apache.org/jira/browse/HDFS-13032?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tao Jie updated HDFS-13032:
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Attachment: HDFS-13032.002.patch
> Make AvailableSpaceBlockPlacementPolicy more adaptive
> -----------------------------------------------------
>
> Key: HDFS-13032
> URL: https://issues.apache.org/jira/browse/HDFS-13032
> Project: Hadoop HDFS
> Issue Type: Improvement
> Affects Versions: 2.8.2
> Reporter: Tao Jie
> Priority: Major
> Attachments: HDFS-13032.001.patch, HDFS-13032.002.patch
>
>
> In a heterogeneous HDFS cluster, datanode capacity and usage are very
> different.
> Now we can use HDFS-8131, a usage-aware block placement policy to deal with
> the problem. However, this policy could be more flexible.
> 1, The probability of a node with high usage being chosen is fixed once the
> parameter is set. That is the probability is always the same no matter its
> usage is 90% or 70%. When the usage of a node is close to full, its
> probability of being chosen should be lower.
> 2, When the difference of usage is below 5%(hard code), the two nodes are
> considered the same usage. I think it's OK when usage is 30% and 35%, but
> when usage is 93% and 98%, they should not be treated equally. The correction
> of probability could be more smooth.
> In my opinion, when we choose one node from two candidates (A: usage 30%, B:
> usage 60%), we can calculate the probability according to the available
> storage. p(A) = 70%/(70% + 40%), p(B) = 40% (70% +40%). When a node is close
> to full, the probability would be very small.
> Also we could have another factor to weaken this correctness, and make the
> modification not so aggressive.
> Any thought? [~liushaohui]
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