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From "Hairong Kuang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1463) dfs.datanode.du.reserved semantics being violated
Date Mon, 10 Mar 2008 20:46:48 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12577174#action_12577174
] 

Hairong Kuang commented on HADOOP-1463:
---------------------------------------

This jira is closed. Please open a new jira if you think there is a bug.

Reserved space is considered in the first statement when calculating remaining. The reserved
space is for non-dfs usage including map/reduce, other applications, and unusable disk space
on a partition etc. Only when non-dfs usage is more than the reserved space, remaining is
set to be the the available space on the disk.

> dfs.datanode.du.reserved semantics being violated
> -------------------------------------------------
>
>                 Key: HADOOP-1463
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1463
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.15.3, 0.16.0
>            Reporter: Hairong Kuang
>            Assignee: Hairong Kuang
>            Priority: Blocker
>             Fix For: 0.15.0
>
>         Attachments: usedSpace.patch, 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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