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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1463) dfs should report total size of all the space that dfs is using
Date Tue, 26 Jun 2007 19:38:26 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1463?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12508301
] 

Doug Cutting commented on HADOOP-1463:
--------------------------------------

> run "df" when datanode gets started to get the data node's disk space and the reserved
space

We should also run "df" periodically, since other applications may be using disk space too
(like MapReduce).  Probably once-per-heartbeat is excessive, but not less than once every
few minutes.

> 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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