Thank you Date: Thu, 20 Jan 2011 09:26:36 -0800 From: ayonsi...@yahoo.com Subject: Re: Adding new data nodes to existing cluster, with different storage capcity To: hdfs-user@hadoop.apache.org
We did the same exercise a few months back. When we run the balancer which takes a while to balance, it will balance based on the percentage of disk usage on each node, so you will end up with usage of nodes between say 45-55% on all nodes.Sometimes the balancer does not balance well initially, in which case, we increased the rep factor to 4 and kept it that way for a few day while running the balancer. Then we brought down the rep factor back to 3 and let the balancer run. -Ayon From: David Ginzburg <ginz...@hotmail.com> To: HDFS USER mail list <hdfs-user@hadoop.apache.org> Sent: Thu, January 20, 2011 12:42:17 AM Subject: Adding new data nodes to existing cluster, with different storage capcity Hi, Our current cluster runs with 22 data nodes - each with 4TB . We should be installing new data nodes on this existing cluster , but each will have 8TB of storage capacity. I am wondering how will the namenode distribute the blocks, It is my understanding that Replica Placement policy is that data nodes are chosen at random, so an even distribution is expected , So eventually the smaller nodes will fill up while the larger nodes will reach 50% at which point the small nodes will become unusable. Am I correct? Is there any recommended practice in this case? would running a balancer periodically help?