@Riccardo Iacomini, are you asking about the HDFS move/rename command? Move is purely a metadata operation on the NameNode and does not result in any data movement until the HDFS Mover utility is run. https://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-hdfs/ArchivalStorage.html#Mover_-_A_New_Data_Migration_Tool Edit: The Mover will move blocks within the same node when possible and thus try to avoid network activity. If that is not possible (e.g. when a node doesn't have SSD or when the local SSDs are full), it will move block replicas across the network to another node that has the target media. ... View more

These pages are still present. You can navigate to the jmx servlet on the DataNode web UI. e.g. http://<datanode>:50075/jmx ... View more

Hi @JJ Tsien, 1. We don't support setting quotas via a configuration file. Quotas must be set using the setQuota command issued by an administrator. 2. There is no way to specify quotas as a percentage of total storage either, sorry. ... View more

@Viswa, the Apache documentation provides a good description. https://hadoop.apache.org/docs/r2.7.3/hadoop-project-dist/hadoop-hdfs/HdfsUserGuide.html#Secondary_NameNode I have never seen Checkpoint/Backup node being used in practice and these should be considered deprecated. I recommend using the Secondary NameNode. Ideally you should use NameNode HA which eliminates the single point of failure. https://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-hdfs/HDFSHighAvailabilityWithQJM.html If you use Ambari to install HDP, SecondaryNameNode is enabled by default and NameNode HA can be enabled using a wizard. ... View more

Hi @Akash S, this is a known issue and it is benign. You can safely ignore the alerts. If you want to avoid seeing them you can append the following options to HADOOP_DATANODE_OPTS via Ambari and restart DataNodes. -XX:CMSInitiatingOccupancyFraction=70-XX:+UseCMSInitiatingOccupancyOnly-XX:ConcGCThreads=8-XX:+UseConcMarkSweepGC Also asked here: https://community.hortonworks.com/questions/85961/ambari-alert-datanode-heapsize-alert.html#answer-85964 ... View more

This is a benign issue and the alerts can be safely ignored. It was addressed by AMBARI-18936. You can fix it by manually adding the following options to HADOOP_DATANODE_OPTS via Ambari: -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSInitiatingOccupancyOnly -XX:ConcGCThreads=8 -XX:+UseConcMarkSweepGC ... View more

Commenting to clarify that some of the advice above is not wrong but it can be dangerous. Starting with HDP 2.2 and later, the DataNode is more strict about where it expects block files to be. I do not recommend moving block files or folders on DataNodes around manually, unless you really know what you are doing. @jovan karamacoski, to answer your original question - the NameNode drives the re-replication (specifically the BlockManager class within the NameNode). The ReplicationMonitor thread wakes up periodically and computes re-replication work for DataNodes. The re-replication logic has multiple triggers like block reports, heartbeat timeouts, decommission etc. ... View more

The question is unclear to me but I recommend reading the following three blog posts carefully as they go into great detail about balancer basics, configuration and best practices: https://community.hortonworks.com/articles/43615/hdfs-balancer-1-100x-performance-improvement.html https://community.hortonworks.com/articles/43849/hdfs-balancer-2-configurations-cli-options.html https://community.hortonworks.com/articles/44148/hdfs-balancer-3-cluster-balancing-algorithm.html ... View more

Hi @ripunjay godhani, we no longer recommend setting up NameNode HA with NFS. Instead please use the Quorum Journal Manager setup. The Apache HA with QJM documentation is a good start: https://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-hdfs/HDFSHighAvailabilityWithQJM.html NameNode image files will be stored on two nodes (active and standby NN) in this setup. The latest edit logs will be on the active NameNode and at least two journal nodes (usually all three, unless one Journal Node has an extended downtime). The NameNodes can optionally be configured to write their edit logs to separate NFS shares if you really want but it is not necessary. You don't need RAID 10. HDFS HA with QJM provides good durability and availability with commodity hardware. ... View more

@sgowda, thanks for confirming you just want to mount volumes at a new location. If you are just remounting then your existing HDFS metadata and data files will be present but under new Linux paths. In that case decommissioning is not necessary. You just need to to update NameNode and DataNode configuration settings like dfs.namenode.name.dir, dfs.datanode.data.dir to point to the new locations. See this link for a full list of settings, not all may apply to you. Don't reformat the NN else you will lose all your data. The simplest approach is: Take a full cluster downtime and bring down all HDFS services. Remount volumes at the new location on all affected nodes. Update NN and DN configurations via Ambari to point to the new storage roots. Restart services. If you are not familiar with these settings I recommend learning more about HDFS first since its easy to lose data via administrative mistakes. ... View more