All replicas for a block end up in same rack --------------------------------------------
Key: HDFS-1480 URL: https://issues.apache.org/jira/browse/HDFS-1480 Project: Hadoop HDFS Issue Type: Bug Reporter: T Meyarivan Priority: Minor It appears that all replicas of a block can end up in the same rack. The likelihood of such replicas seems to be directly related to decommissioning of nodes. Post rolling OS upgrade (decommission 3-10% of nodes, re-install etc, add them back) of a running cluster, all replicas of about 0.16% of blocks ended up in the same rack. Hadoop Namenode UI etc doesn't seem to know about such incorrectly replicated blocks. "hadoop fsck .." does report that the blocks must be replicated on additional racks. Looking at ReplicationTargetChooser.java, following seem suspect: snippet-01: """ int maxNodesPerRack = (totalNumOfReplicas-1)/clusterMap.getNumOfRacks()+2; """ snippet-02: """ if (counter>maxTargetPerLoc) { logr.debug("Node "+NodeBase.getPath(node)+ " is not chosen because the rack has too many chosen nodes"); return false; } """ snippet-03: """ default: chooseRandom(numOfReplicas, NodeBase.ROOT, excludedNodes, blocksize, maxNodesPerRack, results); } """ -- -- This message is automatically generated by JIRA. - You can reply to this email to add a comment to the issue online.