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From "Suresh Srinivas (JIRA)" <j...@apache.org>
Subject [jira] Updated: (HADOOP-4430) Namenode Web UI capacity report is inconsistent with Balancer
Date Mon, 20 Oct 2008 18:13:44 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-4430?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Suresh Srinivas updated HADOOP-4430:
------------------------------------

    Release Note: 
Incompatible changes:
This change modifies/retains the changes made in 2816 as follows:
1) Present Capacity added in 2816 is removed from the Web UI
2) Change of Total Capacity to Configured Capacity and its definition from 2816 is retained
in the Web UI
3) Data node protocol change to report Configured Capacity instead of Total Capacity is retained.
4) DFS Used% was calculated as a percentage of Present Capacity. It is changed to percentage
of Configured Capacity.

Other incompatible changes:
1) Config parameter dfs.datanode.du.pct is no longer used and is removed from the hadoop-default.xml.

2) Namenode Web UI has the following addional changes:
   The following parameters are added to both Cluster Summary and Datanode information:
   * Non DFS Used - This indicates the disk space taken by non DFS file
   * DFS remaining % - This is remaining % of Configured Capacity available for DFS use


  was:
Incompatible changes:
1) Config parameter dfs.datanode.du.pct is no longer used and is removed from the hadoop-default.xml.

2) Namenoe Web UI has the following changes:
   The following parameters are removed:
   * Total Capacity

   The following parameters are added to both Cluster Summary and Datanode information:
   * Configured Capacity - This is total diskspace of all the data directories minus the resereved
capacity defined by 
   * Non DFS Used - This indicates the disk space taken by non DFS file
   * DFS remaining % - This is remaining % of Configured Capacity available for DFS use

   The following parameters are modified:
   * DFS Used % - This is changed from % of Total Capacity to % of Configured Capacity



> Namenode Web UI capacity report is inconsistent with Balancer
> -------------------------------------------------------------
>
>                 Key: HADOOP-4430
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4430
>             Project: Hadoop Core
>          Issue Type: Bug
>          Components: dfs
>    Affects Versions: 0.19.0
>            Reporter: Suresh Srinivas
>            Assignee: Suresh Srinivas
>            Priority: Blocker
>             Fix For: 0.19.0
>
>         Attachments: HADOOP-4430.patch, HADOOP-4430.patch, HADOOP-4430.patch
>
>
> Solution to 2816 changed
> - Total Capacity definition from (the disk space of all data directories) to (the disk
space of all the data directories - the reserved space)
> - We added a new element Present Capacity to the report. It is set to (Used Capacity
+ Remaining Capacity)
> - We changed the Used Percentage reported from (Used Capacity)/(Total Capacity) to (Used
Capacity)/(Present Capacity)
> - All these changes are displayed on Namenode Web UI.
> Balancer functionality
> Balancer script is started with a threshold parameter. It tries to move the blocks from
the nodes that have Used % that is more than (Cluster average + threshold) to the nodes that
have less than (Cluster average - threshold). Essentially balancer gets all the datanodes
used % to with in (the Cluster average +/- threshold).
> Inconsistencies due to the change in 2816
> When MapReduce jobs are run, temporary files are generated. This eats away a lot of space
from Present Capacity. The difference between the Total Capacity and the Present Capacity
can be huge. Currently balancer computes Used Percentage based (Used Capacity)/(Total Capacity).
The Used % the balancer uses could be significantly different from Used % displayed on the
Namenode Web UI. When balancer is done balancing, the Namenode Used % might still appear unbalanced.

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