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.
Cheers, Rich On Jul 1, 2015, at 3:30 AM, Bing Jiang <jiangbinglo...@gmail.com<mailto:jiangbinglo...@gmail.com>> wrote: 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 | rha...@pandora.com<mailto:rha...@pandora.com>
