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https://issues.apache.org/jira/browse/HDFS-8041?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Kihwal Lee resolved HDFS-8041.
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Resolution: Won't Fix
While this jira makes balancing more aggressive when free space is low, there
are corner cases where it can perform poorly.
AvailableSpaceBlockPlacementPolicy might be a better tool. Closing, won't fix.
> Consider remaining space during block blockplacement if dfs space is highly
> utilized
> ------------------------------------------------------------------------------------
>
> Key: HDFS-8041
> URL: https://issues.apache.org/jira/browse/HDFS-8041
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: Kihwal Lee
> Assignee: Kihwal Lee
> Labels: BlockPlacementPolicy
> Attachments: HDFS-8041.v1.patch, HDFS-8041.v2.patch,
> HDFS-8041.v3.patch, HDFS-8041.v4.patch
>
>
> This feature is helpful in avoiding smaller nodes (i.e. heterogeneous
> environment) getting constantly being full when the overall space utilization
> is over a certain threshold. When the utilization is low, balancer can keep
> up, but once the average per-node byte goes over the capacity of the smaller
> nodes, they get full so quickly even after perfect balance.
> This jira proposes an improvement that can be optionally enabled in order to
> slow down the rate of space usage growth of smaller nodes if the overall
> storage utilization is over a configured threshold. It will not replace
> balancer, rather will help balancer keep up. Also, the primary replica
> placement will not be affected. Only the replicas typically placed in a
> remote rack will be subject to this check.
> The appropriate threshold is cluster configuration specific. There is no
> generally good value to set, thus it is disabled by default. We have seen
> cases where the threshold of 85% - 90% would help. Figuring when
> {{totalSpaceUsed / numNodes}} becomes close to the capacity of a smaller node
> is helpful in determining the threshold.
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