What is high availability in NameNode?

The HDFS NameNode High Availability feature enables you to run redundant NameNodes in the same cluster in an Active/Passive configuration with a hot standby. In the case of an unplanned event such as a machine crash, the cluster would be unavailable until an operator restarted the NameNode.

How do I enable high availability?

Enabling HA enables automatic failover as part of the same command….Enabling High Availability and automatic failover

Go to the HDFS service.
Select Actions > Enable High Availability.
Restart Ranger KMS, if configured for your cluster.
Configure HDFS HA for other CDP services, if required.

What is high availability in Hadoop?

The high availability feature in Hadoop ensures the availability of the Hadoop cluster without any downtime, even in unfavorable conditions like NameNode failure, DataNode failure, machine crash, etc. It means if the machine crashes, data will be accessible from another path.

How do I enable high availability in HDFS?

Setting Up and Configuring High Availability Cluster in Hadoop:

Extract the Hadoop tar ball.
Generate the SSH key in all the nodes.
In Active Namenode, copy the id_rsa.
Copy the NameNode public key to all the nodes using ssh-copy-id command.
Copy NameNode public key to data node.

What is the difference between a federation and high availability?

The main difference between HDFS High Availability and HDFS Federation would be that the namenodes in Federation aren’t related to each other. While in case of HDFS HA, there are two namenodes – Primary NN and Standby NN.

What is a secondary NameNode?

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 is high availability setup?

HA configuration overview The purpose of an HA configuration is to reduce downtime when a zone or instance becomes unavailable. With HA, your data continues to be available to client applications. The HA configuration, sometimes called a cluster, provides data redundancy.

How does NameNode tackle Datanode failures and ensures high availability?

Namenode periodically receives a heartbeat and a Block report from each Datanode in the cluster. Since blocks will be under replicated, the system starts the replication process from one Datanode to another by taking all block information from the Block report of corresponding Datanode.

What is the main problem faced while reading and writing data in parallel from multiple disks?

Answer : D. Q 4 – What is the main problem faced while reading and writing data in parallel from multiple disks? A – Processing high volume of data faster.

What helps with multiple Namenode?

x provides support for multiple NameNodes/namespaces. This overcomes the isolation, scalability, and performance limitations of the prior HDFS architecture. HDFS Federation architecture also opens up the architecture for future innovations. It allows new services to use block storage directly.

What is the problem with secondary 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. As the NameNode is the single point of failure in HDFS, if NameNode fails entire HDFS file system is lost.

What does HDFS high availability mean for NameNode?

HDFS NameNode High Availability architecture provides the option of running two redundant NameNodes in the same cluster in an active/passive configuration with a hot standby. Active NameNode – It handles all client operations in the cluster. Passive NameNode – It is a standby namenode,…

When to use active and standby namenode in Hadoop?

Active and Standby NameNode should always be in sync with each other, i.e. they should have the same metadata. This permit to reinstate the Hadoop cluster to the same namespace state where it got crashed. And this will provide us to have fast failover. There should be only one NameNode active at a time.

What happens when a Name node fails in Hadoop?

Prior to Hadoop 2.0.0, the NameNode was a single point of failure (SPOF) in an HDFS cluster. Each cluster had a single NameNode, and if that machine or process became unavailable, the cluster as a whole would be unavailable until the NameNode was either restarted or brought up on a separate machine.

Why was high availability added to Hadoop 2.x?

High Availability was a new feature added to Hadoop 2.x to solve the Single point of failure problem in the older versions of Hadoop. As the Hadoop HDFS follows the master-slave architecture where the NameNode is the master node and maintains the filesystem tree. So HDFS cannot be used without NameNode.