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From Rich Haase <rha...@pandora.com>
Subject Re: Move blocks between Nodes
Date Wed, 01 Jul 2015 15:09:04 GMT
Hi Bing,

I would recommend that you add your 50 new nodes to the cluster and the decommission the 50
nodes you want to get rid of.  You can do the decommission in one operation (albeit a lengthy
operation) by adding the nodes you want to decommission to your HDFS exclude file and running
`hdfs dfsadmin -refreshNodes`.  The decommission process will ensure that the data from your
old nodes are distributed across your cluster.



On Jul 1, 2015, at 3:30 AM, Bing Jiang <jiangbinglover@gmail.com<mailto:jiangbinglover@gmail.com>>

hi, guys.

I want to move all the blocks from 50 datanodes to another 50 new datanodes. There is a very
easy idea that we can add the new 50 nodes to hadoop cluster firstly, then decommission the
other 50 nodes one by one. But, I believe it is not an efficient way to reach the goal.
So I plan to get the help of  the idea of Hdfs balancer, which limits the movements  happen
to the 100 nodes. But I need to disable write_op for those nodes to be decommissioned.

Is there a way to make DataNode in safe mode (read only) mode?

Of course, regarding to blocks movement between nodes,  Any thoughts will be appreciated.

Bing Jiang

Rich Haase| Sr. Software Engineer | Pandora
m (303) 887-1146 | rhaase@pandora.com<mailto:rhaase@pandora.com>

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