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https://issues.apache.org/jira/browse/HADOOP-1463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12511871
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Koji Noguchi commented on HADOOP-1463:
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> From my understanding dfs.datanode.du.pct and dfs.datanode.du.reserved are
> two different ways of specifying reserved space.
>
I used to think the same. But there shouldn't be two config variables that
serve the same purpose.
So, assuming "dfs.datanode.du.reserved" is the one for "space reserved for
non-dfs usage *whether it is used or unused*"
I'd want
{noformat}
MIN( Total_Capacity - cur_space_used_by_Datanode - dfs.datanode.du.reserved,
cur_disk_available)
{noformat}
I'm not sure where "dfs.datanode.du.pct" should fit. Maybe
{noformat}
MIN( Total_Capacity - cur_space_used_by_Datanode - dfs.datanode.du.reserved,
cur_disk_available) * dfs.datanode.du.pct
{noformat}
> dfs should report total size of all the space that dfs is using
> ---------------------------------------------------------------
>
> Key: HADOOP-1463
> URL: https://issues.apache.org/jira/browse/HADOOP-1463
> Project: Hadoop
> Issue Type: Improvement
> Components: dfs
> Affects Versions: 0.12.3
> Reporter: Hairong Kuang
> Assignee: Hairong Kuang
> Fix For: 0.14.0
>
>
> Currently namenode reports two statistics back to the client:
> 1. The total capacity of dfs. This is a sum of all datanode's capacities,
> each of which is calculated by datanode summing all data directories disk
> space.
> 2. The total remaining space of dfs. This is a sum of all datanodes's
> remaining space. Each datanode's remaining space is calculated by using the
> following formula: remaining space = unused space -
> capacity*unusableDiskPercentage - reserved space. So the remaining space
> shows how much space that the dfs can still use, but it does not show the
> size of unused space.
> Each dfs client caculates the total dfs used space by substracting remaining
> space from the total capacity. So the used space does not accurately shows
> the space that dfs is using. However it is a very important number that dfs
> should provide.
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