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Rodrigo Schmidt commented on HDFS-1094: --------------------------------------- The higher the number of racks, the higher the latency for the write pipeline. Otherwise, the default block placement policy would use 3 different racks always instead of always having 2 replicas on the same rack. I've had some general discussions with Dhruba about the balancer. It doesn't use the block placement policy, so I'll have to extend it separately. > Intelligent block placement policy to decrease probability of block loss > ------------------------------------------------------------------------ > > Key: HDFS-1094 > URL: https://issues.apache.org/jira/browse/HDFS-1094 > Project: Hadoop HDFS > Issue Type: Improvement > Components: name-node > Reporter: dhruba borthakur > Assignee: Rodrigo Schmidt > Attachments: prob.pdf, prob.pdf > > > The current HDFS implementation specifies that the first replica is local and > the other two replicas are on any two random nodes on a random remote rack. > This means that if any three datanodes die together, then there is a > non-trivial probability of losing at least one block in the cluster. This > JIRA is to discuss if there is a better algorithm that can lower probability > of losing a block. -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.