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https://issues.apache.org/jira/browse/HDFS-11257?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15768527#comment-15768527
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Inigo Goiri commented on HDFS-11257:
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[~andrew.wang], thanks for the feedback.
There are a couple situations where my proposal might make more sense:
* Windows systems where such functionality is not native.
* Not dedicated HDFS clusters. We have some machines where DNs share the disk
space with other services that have priority.
Regarding the reserved, I agree, we internally implemented such feature too.
We actualy use both at the same time.
> Evacuate DN when the remaining is negative
> ------------------------------------------
>
> Key: HDFS-11257
> URL: https://issues.apache.org/jira/browse/HDFS-11257
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 2.7.3
> Reporter: Inigo Goiri
>
> Datanodes have a maximum amount of disk they can use. This is set using
> {{dfs.datanode.du.reserved}}. For example, if we have a 1TB disk and we set
> the reserved to 100GB, the DN can only use ~900GB. However, if we fill the DN
> and later other processes (e.g., logs or co-located services) start to use
> the disk space, the remaining space will go to a negative and the used
> storage >100%.
> The Rebalancer or decommissioning would cover this situation. However, both
> approaches require administrator intervention while this is a situation that
> violates the settings. Note that decommisioning, would be too extreme as it
> would evacuate all the data.
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