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https://issues.apache.org/jira/browse/HADOOP-1463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12513154
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Koji Noguchi commented on HADOOP-1463:
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bq. The current implementation is interpreted the reserved space as the space
reserved per volume. We want it to be the space reserved per datanode, right?
I'm sorry that I missed this.
At least for me, I'd like to reserve the space for each volume so that
mapreduce can utilize multiple drives.
bq. 1. datanode sends namenode (dfs used space + remaining space, remaining
space) per heartbeat.
Namenode webUI as well as the "dfsadmin -report" now show "total (dfs used
space + remaining space)" as the 'capacity'. This might be more accurate as the
dfs capacity, but maybe it'll confuse the users?
If reserved space is set to 0, capacity will keep on changing as mapreduce uses
those spaces.
Can I ask for
o Capacity (df total)
o DFS Used
o DFS Remaining ?
> 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
>
> Attachments: usedSpace.patch
>
>
> 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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