Big Data&Hadoop Interview Questions and Answers

What is Big Data?

Big information could be a term that describes the large and complicated information (i.e Structured, Semi-structured and Unstructured) that it becomes terribly tedious to capture, store, process, retrieve and analyze exploitation ancient information and code techniques.

What are the five V’s (characteristics) of massive Data?

Big information has 5 main characteristics:

  • Volume – Volume describes the number of information generated by organizations or people.
  • speed – speed describes the frequency at that information is generated, captured and shared.
  • selection – selection refers to differing types of information i.e. structured, semi-structured and unstructured information that is text, video, audio, sensing element information, log files etc.
  • truthfulness -Veracity refers to the messiness or trait of the info.
  • price – price refers to our ability flip our information into price.

What is Hadoop?

Hadoop is code framework or platform that permits for distributed storage and distributed process of terribly giant information sets on pc clusters.

Hadoop = HDFS + Map cut back

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What are options of Hadoop?

Fault Tolerance – By default three replicas of every block is keep across the cluster in Hadoop and it may be modified conjointly as per the necessity. therefore if any node goes down, information on it node may be recovered from alternative nodes simply. Failures of nodes or tasks are recovered mechanically by the framework.

Reliability – as a result of replication of information within the cluster, information is faithfully keep on the cluster of machine despite machine failures. If your machine goes down, then conjointly your information are keep faithfully.

High handiness – High handiness (HA) refers to the aptitude of a Hadoop system to continue functioning, no matter multiple system failures. If a machine or few hardware crashes, then information are accessed from another path.

Scalability – Hadoop could be a extremely climbable storage platform as a result of it will store and distribute terribly giant information sets across many cheap servers that operate in parallel. Hadoop is extremely climbable within the means new hardware may be simply additional to the nodes. It conjointly provides horizontal quantifiability which implies new nodes may be additional on the fly with none period.

Economic – Hadoop isn’t terribly dear because it runs on the cluster of artefact hardware. we tend to don’t would like any specialised machine for it. Hadoop provides Brobdingnagian price saving conjointly because it is extremely simple to feature additional nodes on the fly here. Therefore if demand will increase, you’ll be able to increase nodes additionally with none period and while not requiring a lot of pre-planning.

Data neighbourhood – Hadoop works on information neighbourhood principle that states that move computation to information rather than information to computation. once the shopper submits the algorithmic rule, this algorithmic rule is affected to information within the cluster instead of delivery information to the situation wherever Associate in Nursing algorithmic rule is submitted then process it.

Flexibility – Hadoop manages information whether or not structured, semi-structured or unstructured, encoded or formatted, or the other kind of information.

What is the essential distinction between ancient RDBMS and Hadoop?

Hadoop Core does not support time period processing (OLTP), it’s designed to support large-scale instruction execution workloads (OLAP), whereas RDBMS are designed for OLTP (Real-time information processing) not instruction execution.

Hadoop is Associate in Nursing approach to store the large quantity of information within the distributed filing system and method it, whereas RDBMS is employed for transactional systems to report and archive the info.

Hadoop framework works all right with structured and unstructured information. This conjointly supports the range of information formats in real time like XML, JSON and text-based file formats. However, RDBMS solely work with higher once Associate in Nursing entity relationship model (ER model) is outlined utterly and so, the information schema or structure will grow and unmanaged otherwise.i.e. Associate in Nursing RDBMS works well with structured information.

What is the distinction between Hadoop one and Hadoop 2?

Hadoop 1.x

Hadoop 2.x

In Hadoop one.x, “Namenode” has Single-Point-of-Failure (SPOF) due to single Namenode.

In Hadoop a pair of.x, there are Active and Passive (standby) “Namenodes”. If the active Namenode fails, the passive “Namenode” takes charge. due to this High handiness may be achieved.

Supports MapReduce (MR) process model solely.

Allows operating in Mr additionally as alternative distributed computing models like Spark, HBase coprocessors etc.

MR will each process and cluster resource management.

YARN (Yet Another Resource Negotiator) will cluster resource management and process is completed exploitation totally different process models.

A single Namenode to manage the complete namespace.

Multiple Namenode servers manage multiple namespaces.

What are the core parts of Hadoop?

Core parts of Hadoop are HDFS and MapReduce.

HDFS {is basically|is essentially|is giantly} accustomed store large datasets.

MapReduce is employed to method such giant datasets.

How does one outline “block” in HDFS? What’s the block size in Hadoop one and Hadoop 2? Will or not it’s changed?

A “block” is that the minimum quantity of information which will be browse or written. it’s a storage entity of HDFS. Files in HDFS are weakened into block-sized chunks, that are keep as freelance units.

In Hadoop one, default block size is 64MB

In Hadoop a pair of, default block size is 128MB

Yes, block size may be modified. The dfs.block.size parameter may be employed in hdfs-site.xml file to line the scale of a block in an exceedingly Hadoop surroundings.

What is Block Scanner in HDFS?

Block scanner maintains the integrity of the info blocks. It runs sporadically on each Datanode to verify whether or not the info blocks keep are correct or not.


Datanode reports to Namenode.

Namenode schedules the creation of recent replicas exploitation the great replicas.

Once the replication issue (uncorrupted replicas) reaches to the specified level, deletion of corrupted blocks takes place.

What is a Daemon?

Daemon may be a method or service that runs within the background. In general, we have a tendency to use this word in OS setting. The equivalent of Daemon in Windows is “services”.

What are the modes Hadoop will run in?

Hadoop will run in 3 totally different modes-

Local/Standalone Mode

  1. This is often the only method mode of Hadoop, that is that the default mode, whereby that no daemons are running.
  2. This mode is beneficial for testing and debugging.

Pseudo Distributed Mode

  1. This mode may be a simulation of totally distributed mode however on single machine. This suggests that,    all the daemons of Hadoop can run as a separate method.
  2. This mode is beneficial for development.

Fully Distributed Mode

  1. This mode needs 2 or a lot of systems as cluster.
  2. Name Node, knowledge Node and every one the processes run on totally different machines within the cluster.

iii. This mode is beneficial for the assembly setting.

Tell US however massive knowledge and Hadoop are associated with one another

Massive knowledge and Hadoop are nearly synonyms terms. With the increase of huge knowledge, Hadoop, a framework that focuses on massive knowledge operations conjointly became common. The framework may be employed by professionals to research massive knowledge and facilitate businesses to create choices.

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However is massive knowledge analysis useful in increasing business revenue?

Massive knowledge analysis has become vital for the companies. It helps businesses to differentiate themselves from others and increase the revenue. Through prophetical analytics, massive knowledge analytics provides businesses customised recommendations and suggestions. Also, massive knowledge analytics permits businesses to launch new merchandise looking on client wants and preferences. These factors build businesses earn a lot of revenue, and therefore firms are exploitation massive knowledge analytics. Firms could encounter increase of 5-20% in revenue by implementing big knowledge analytics. Some common firms those are exploitation massive knowledge analytics to extend their revenue is – Walmart, LinkedIn, Facebook, Twitter, Bank of America etc.

Make a case for the steps to be followed to deploy a giant knowledge resolution.

Followings are the 3 steps that are followed to deploy a giant knowledge resolution –

Knowledge activity

The first step for deploying a giant knowledge resolution is that the knowledge activity i.e. extraction of information from numerous sources. the information supply could also be a CRM like Salesforce, Enterprise Resource designing System like SAP, RDBMS like MySQL or the other log files, documents, social media feeds etc. the information may be eaten either through batch jobs or period streaming. The extracted knowledge is then keep in HDFS.

Big knowledge Interview queries and Answers

Steps of deploying massive knowledge resolution

Knowledge Storage

After knowledge activity, succeeding step is to store the extracted knowledge. the information either be keep in HDFS or NoSQL information (i.e. HBase). The HDFS storage works well for consecutive access whereas HBase for random read/write access.


The final step in deploying a giant knowledge resolution is that the processing. the information is processed through one in every of the process frameworks like Spark, MapReduce, Pig, etc.