I wasn't able to get decommissioning to work at all and found that just taking 
the node down got it out of the cluster. What version are you running and how 
are you initiating the decommissioning?

-Rob


Rob Hamilton - VP Network Operations 
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E [email protected]   
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-----Original Message-----
From: Hargraves, Alyssa [mailto:[email protected]] 
Sent: Wednesday, January 21, 2009 7:35 PM
To: [email protected]
Subject: Decommissioning Nodes

Hello Hadoop Users,

I was hoping someone would be able to answer a question about node 
decommissioning.  I have a test Hadoop cluster set up which only consists of my 
computer and a master node.  I am looking at the removal and addition of nodes. 
 Adding a node is nearly instant (only about 5 seconds), but removing a node by 
decommissioning it takes a while, and I don't understand why. Currently, the 
systems are running no map/reduce tasks and storing no data. DFS Health reports:

7 files and directories, 0 blocks = 7 total. Heap Size is 6.68 MB / 992.31 MB 
(0%)
Capacity        :       298.02 GB
DFS Remaining   :       245.79 GB
DFS Used        :       4 KB
DFS Used%       :       0 %
Live Nodes      :       2
Dead Nodes      :       0

Node     Last Contact    Admin State     Size (GB)       Used (%)        Used 
(%)        Remaining (GB)          Blocks
master  0       In Service      149.01  0       
        122.22  0
slave   82      Decommission In Progress        149.01  0       
        123.58  0 

However, even with nothing stored and nothing running, the decommission process 
takes 3 to 5 minutes, and I'm not quite sure why. There isn't any data to move 
anywhere, and there aren't any jobs to worry about.  I am using 0.18.2.

Thank you for any help in solving this,
Alyssa Hargraves

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