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From David Ginzburg <ginz...@hotmail.com>
Subject RE: Rack decommission
Date Thu, 03 May 2012 15:04:33 GMT

I have began decommissioning the servers  in the rack.
When I view the "dfsnodelist.jsp?whatNodes=DECOMMISSIONING"  page, there are many slaves with
"Blocks With No Live Replicas"
Is it possible , even if I have rack awareness configured ? 

From: ginzman@hotmail.com
To: hdfs-user@hadoop.apache.org; common-user@hadoop.apache.org
Subject: Rack decommission
Date: Wed, 2 May 2012 11:49:41 +0000


I have a cluster with 4 racks.
I am scheduled to replace one of them, with slave servers included.
The cluster is configured with rack awareness and replication factor is 3.
It is my understanding that on rack aware clusters, block placement policy ensures blocks
are at least on two racks.
I am concerned about decommission of whole rack.

I considered decommission each node in the rack separately and let it balance automatically
 , but I am afraid it will take a lot of time.

If a DN is decommissioned and returns, Does the NM update it's block meta data. If it does,
 How does it decide when to update the meta data map?

Is there a suggested way to decommission a whole rack , I may have missed?

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