What is a namenode in hadoop

what is a namenode in hadoop

What is the Difference Between NameNode and DataNode in Hadoop

What is NameNode in Hadoop? NameNode is the foundation of the HDFS system. It stores all the directory tree of the files in a single file system and keeps track of where the data file is kept. It does not store the data within itself. NameNode is a single point of failure in Hadoop cluster. NameNode is usually configured with a lot of memory (RAM). Because the block locations are help in main memory.

The main difference between NameNode and DataNode in Hadoop is that the NameNode is the master node in Hadoop Distributed File System that manages the file system metadata while the DataNode is a slave node in Hadoop distributed file system that stores the actual data as instructed by the NameNode. Hadoop is an open source framework developed by Apache Software Foundation. It allows storing and processing a large amount of data simultaneously across clusters of computers in a distributed environment.

HDFSon the other hand, is the distributed file system of Hadoop, which distributes data over multiple machines and replicates them to increase durability, reliability, and availability. Moreover, HDFS works according to master-slave architecture. Namenode and dataNode are components of this architecture.

What is NameNode — Definition, Functionality 2. What is DataNode — Definition, Functionality 3. Metadata refers to a small amount of data, and it requires a minimum amount of memory to store. Namenode stores this metadata of all the files in HDFS.

Metadata includes file permission, names, and location of each block. A block is a minimum amount of data that can be read or write. Moreover, NameNode maps these blocks to dataNodes. Furthermore, nameNode manages all other dataNodes. Master node is an alternative name for nameNode.

The call it what you want sheet music other than the nameNode are called dataNodes. Slave node is another name for dataNode. The data nodes store and retrieve blocks as instructed by the nameNode. All dataNodes continuously communicate with the iphone on recovery mode how to fix it node. They also inform the nameNode about the blocks they are storing.

Furthermore, the dataNodes also perform block creation, deletion, and replication as instructed by the nameNode.

In brief, NameNode controls and manages a single or multiple data nodes. She is passionate about sharing her knowldge in the areas of programming, data science, and computer systems.

View all posts. Leave a Reply Cancel reply.

Your Answer

Namenode is master daemon process of HDFS. It keeps information about file system stored in HDFS. The information is meta data about files and directories. It is important to note that actual data of HDFS files are stored on Data nodes in form of blocks. NameNode is the single point of failure in a Hadoop cluster. Though the loss of any other machine (intermittently or permanently) does not result in data loss because of data replication, NameNode loss results in cluster unavailability. The permanent loss of NameNode data . Oct 22,  · The NameNode is the centerpiece of an HDFS file system. NameNode manages the file system namespace by storing information about the file system tree which contains the metadata about all the files and directories in the file system tree.

If you are new to Hadoop, we suggest to take the free course. Hardware configuration of nodes varies from cluster to cluster and it depends on the usage of the cluster. In Some Hadoop clusters the velocity of data growth is high, in that instance more importance is given to the storage capacity.

If the SLAs for the job executions are important and can not be missed then more importance is give to the processing power of nodes. Commodity Computers or Nodes does not mean cheap or less powerful hardware, it just means in-expensive computer and deemphasize the need for specialized hardware. Here is a sample configuration for NameNode and DataNode hardware configuration. Like what you are reading? NameNode 2. DataNode 3. JobTracker 4. TaskTracker 5.

ResourceManager MRv2 6. ApplicationMaster MRv2 7. NodeManager MRv2 8. SecondaryNameNode etc.. NameNode and DataNode. How to change default replication factor?

July 3, JobTracker and TaskTracker July 14, Categories Hadoop. What is HDFS? NameNode is also known as the Master NameNode only stores the metadata of HDFS — the directory tree of all files in the file system, and tracks the files across the cluster.

NameNode does not store the actual data or the dataset. The data itself is actually stored in the DataNodes. With this information NameNode knows how to construct the file from blocks. NameNode is a single point of failure in Hadoop cluster. NameNode is usually configured with a lot of memory RAM. Because the block locations are help in main memory. When a DataNode starts up it announce itself to the NameNode along with the list of blocks it is responsible for.

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. Because the actual data is stored in the DataNode. Hardware Configuration Hardware configuration of nodes varies from cluster to cluster and it depends on the usage of the cluster. Collectively we have seen a wide range of problems, implemented some innovative and complex or simple, depending on how you look at it big data solutions on cluster as big as nodes.

Related posts. Read more. How to properly remove a node from a Hadoop cluster? How to recursively list files and directories in HDFS?

July 19, at am. September 23, at pm. March 25, at am.

More articles in this category:
<- How to make subtitles in sync with video vlc - How to create zone in brocade switch cli->

3 thoughts on “What is a namenode in hadoop”

Add a comment

Your email will not be published. Required fields are marked *