What is the importance of NameNode?

NameNode is the centerpiece of HDFS. NameNode only stores the metadata of HDFS – the directory tree of all files in the file system, and tracks the files across the cluster. 3. NameNode does not store the actual data or the dataset.

What is the role of NameNode and DataNode in Hadoop?

The NameNode keeps an image of the entire file system namespace and file Blockmap in memory. The DataNode stores HDFS data in files in its local file system. The DataNode has no knowledge about HDFS files. It stores each block of HDFS data in a separate file in its local file system.

What is data node?

A data node is an appliance that you can add to your event and flow processors to increase storage capacity and improve search performance. Each data node can be connected to only one processor, but a processor can support multiple data nodes.

What is the difference between a NameNode and a secondary NameNode?

Name node is the one which stores the information of HDFS filesystem in a file called FSimage. Any changes that you make in your HDFS are never logged directly into FSimage. instead, they are logged into a separate temporary file. This temporary file which stores the intermediate data is called Secondary name node.

What is a data node?

It is the name of the background process which runs on the slave node.It is responsible for storing and managing the actual data on the slave node. The client writes data to one slave node and then it is responsibility of Datanode to replicates data to the slave nodes according to replication factor.

What if NameNode fails in Hadoop?

If NameNode gets fail the whole Hadoop cluster will not work. Actually, there will not any data loss only the cluster work will be shut down, because NameNode is only the point of contact to all DataNodes and if the NameNode fails all communication will stop.

What is a node in big data?

A node is a process running on a virtual or physical machine or in a container. That would be suitable for, say, installing Hadoop on one machine just to learn it. When you run Hadoop in local node it writes data to the local file system instead of HDFS (Hadoop Distributed File System).

What is primary NameNode?

NameNode is the heart of HDFS. NameNode maintains the metadata of HDFS – files, list of blocks, directories, permissions etc. The metadata is persisted on a file named FSIMAGE. During the start up of NameNode, the FSIMAGE file will be read and loaded into memory.

What is secondary NameNode Hadoop?

Secondary NameNode in hadoop is a specially dedicated node in HDFS cluster whose main function is to take checkpoints of the file system metadata present on namenode. It just checkpoints namenode’s file system namespace. The Secondary NameNode is a helper to the primary NameNode but not replace for primary namenode.

What can you infer about NameNode?

Namenode stores metadata of actual data like Filename, path, number of data blocks, block IDs, block location, number of replicas and other slave related informations. Namenode manages all the request(read, write) of client for actual data file.