What is DFS NameNode name DIR?
dfs use. dfs.namenode.name.dir file://${hadoop.tmp.dir}/dfs/name Determines where on the local. filesystem the DFS name node should store. the name. table. (fsimage). If this is a comma-delimited.
Where is DFS Datanode dir?
datanode. data. dir can be any directory which is available on the datanode. It can be a directory where disk partitions are mounted like ‘/u01/hadoop/data, /u02/hadoop/data’ which is in case if you have multiple disks partitions to be used for hdfs purpose.
What is HDFS NameNode?
The NameNode is the centerpiece of an HDFS file system. It keeps the directory tree of all files in the file system, and tracks where across the cluster the file data is kept. The NameNode responds the successful requests by returning a list of relevant DataNode servers where the data lives.
Where is Hadoop tmp dir?
dir is set by default to “${hadoop. tmp. dir}/mapred/system” , and this defines the Path on the HDFS where where the Map/Reduce framework stores system files.
What is FS defaultFS?
The fs. defaultFS makes HDFS a file abstraction over a cluster, so that its root is not the same as the local system’s. You need to change the value in order to create the distributed file system.
What is DFS replication?
DFS Replication enables you to replicate folders between multiple servers. To allow efficient use of the network, it propagates only the changes, uses compression, and uses scheduling to replicate the data between the servers. A replication group can have up to 256 members with 256 replicated folders.
How do you start a DataNode?
Start the DataNode on New Node. Datanode daemon should be started manually using $HADOOP_HOME/bin/hadoop-daemon.sh script. Master (NameNode) should correspondingly join the cluster after automatically contacted. New node should be added to the configuration/slaves file in the master server.
What is DataNode and name node?
DataNode is responsible for storing the actual data in HDFS. When a DataNode is down, it does not affect the availability of data or the cluster. NameNode will arrange for replication for the blocks managed by the DataNode that is not available. DataNode is usually configured with a lot of hard disk space.
What is name node and DataNode in HDFS?
Conclusion. The main difference between NameNode and DataNode in Hadoop is that the NameNode is the master node in HDFS that manages the file system metadata while the DataNode is a slave node in HDFS that stores the actual data as instructed by the NameNode.
What is Hadoop tmp dir used for?
hadoop. tmp. dir is used as the base for temporary directories locally, and also in HDFS. mapred.
What is core site XML file in Hadoop?
The core-site. xml file informs Hadoop daemon where NameNode runs in the cluster. It contains the configuration settings for Hadoop Core such as I/O settings that are common to HDFS and MapReduce.
Which utility is used for checking the health of a HDFS file system?
HDFS fsck is used to check the health of the file system, to find missing files, over replicated, under replicated and corrupted blocks.
Can a NameNode be used as a backup node?
The NameNode allows multiple Checkpoint nodes simultaneously, as long as there are no Backup nodes registered with the system. Backup node: An extension to the Checkpoint node.
Which is the NameNode for the RPC server?
dfs.namenode.rpc-address for the RPC server. It can also be specified per name node or name service for HA/Federation. This is most useful for dfs.namenode.servicerpc-addressRPC address for HDFS Services communication. connecting to this address if it is configured. In the case of HA/Federation where multiple namenodes exist,
How does the secondary namenode work in Apache Hadoop?
The secondary NameNode stores the latest checkpoint in a directory which is structured the same way as the primary NameNode’s directory. So that the check pointed image is always ready to be read by the primary NameNode if necessary.
How does refreshnode update the name of the DataNode?
-refreshNodes: Updates the namenode with the set of datanodes allowed to connect to the namenode. By default, Namenodes re-read datanode hostnames in the file defined by dfs.hosts, dfs.hosts.exclude Hosts defined in dfs.hosts are the datanodes that are part of the cluster.