What is Hadoop? Introduction to Big Data & Hadoop

As to understand what exactly is Hadoop, we have to first understand the issues related to Big Data and the traditional processing system. Advancing ahead, we will discuss what is Hadoop, and how Hadoop is a solution to the problems associated with Big Data. We will also look at the CERN case study to highlight the benefits of using Hadoop. For further details, refer to the Hadoop Certification.

In the previous blog i.e. Big Data Tutorial, we already discussed about Big Data in detail and the challenges with Big Data. In this blog, we are going to discuss:

• Problems with Traditional Approach
• Evolution of Hadoop
• Hadoop
• Hadoop-as-a Solution
• When to use Hadoop?
• When not to use Hadoop?
• CERN Case Study

Big Data is emerging as an opportunity for organizations. Now, organizations have realized that they are getting lots of benefits by Big Data Analytics, as you can see in the below image. They are examining large data sets to uncover all hidden patterns, unknown correlations, market trends, customer preferences and other useful business information.

These analytical findings are helping organizations in more effective marketing, new revenue opportunities, better customer service. They are improving operational efficiency, competitive advantages over rival organizations and other business benefits. 

Figure: What is Hadoop – Benefits of Big Data Analytics

So, let us move ahead and know the problems associated with traditional approach in en-cashing Big data opportunities.

Problems with Traditional Approach 

In traditional approach, the main issue was handling the heterogeneity of data i.e. structured, semi-structured and unstructured. The RDBMS focuses mostly on structured data like banking transaction, operational data etc. and Hadoop specializes in semi-structured, unstructured data like text, videos, audios, Facebook posts, logs, etc. RDBMS technology is a proven, highly consistent, matured systems supported by many companies. While on the other hand, Hadoop is in demand due to Big Data, which mostly consists of unstructured data in different formats.

Now let us understand what are the major problems associated with Big Data. So that, moving ahead we can understand how Hadoop emerged as a solution.

Figure: What is Hadoop – Problems with Big Data

The first problem is storing the colossal amount of data.

Storing this huge data in a traditional system is not possible. The reason is obvious, the storage will be limited only to one system and the data is increasing at a tremendous rate.

Second problem is storing heterogeneous data.

Now, we know storing is a problem, but let me tell you, it is just a part of the problem. Since we discussed that the data is not only huge, but it is present in various formats as well like: Unstructured, Semi-structured and Structured. So, you need to make sure that, you have a system to store all these varieties of data, generated from various sources.

Third problem is accessing and processing speed. 

The hard disk capacity is increasing but the disk transfer speed or the access speed is not increasing at similar rate. Let me explain you this with an example: If you have only one 100 Mbps I/O channel and you are processing 1TB of data, it will take around 2.91 hours. Now, if you have four machines with one I/O channel, for the same amount of data it will take 43 minutes approx. Thus, accessing and processing speed is the bigger problem than storing Big Data.

Before understanding what is Hadoop, let us first look at the evolution of Hadoop over the period of time.

Evolution of Hadoop

In 2003, Doug Cutting launches project Nutch to handle billions of searches and indexing millions of web pages. Later in Oct 2003 – Google releases papers with GFS (Google File System). In Dec 2004, Google releases papers with MapReduce. In 2005, Nutch used GFS and MapReduce to perform operations. In 2006, Yahoo created Hadoop based on GFS and MapReduce with Doug Cutting and team. You would be surprised if I would tell you that, in 2007 Yahoo started using Hadoop on a 1000 node cluster.

Later in Jan 2008, Yahoo released Hadoop as an open source project to Apache Software Foundation. In Jul 2008, Apache tested a 4000 node cluster with Hadoop successfully. In 2009, Hadoop successfully sorted a petabyte of data in less than 17 hours to handle billions of searches and indexing millions of web pages. Moving ahead in Dec 2011, Apache Hadoop released version 1.0. Later in Aug 2013, Version 2.0.6 was available. You can even check out the details of Big Data with the Data Engineering Training in Australia.

When we were discussing about the problems, we saw that a distributed system can be a solution and Hadoop provides the same. Now, let us understand what is Hadoop.

What is Hadoop?

Hadoop is a framework that allows you to first store Big Data in a distributed environment, so that, you can process it parallely. There are basically two components in Hadoop:

Figure: What is Hadoop – Hadoop Framework

The first one is HDFS for storage (Hadoop distributed File System), that allows you to store data of various formats across a cluster. The second one is YARN, for resource management in Hadoop. It allows parallel processing over the data, i.e. stored across HDFS.

Let us first understand HDFS.

HDFS

HDFS creates an abstraction, let me simplify it for you. Similar as virtualization, you can see HDFS logically as a single unit for storing Big Data, but actually you are storing your data across multiple nodes in a distributed fashion. HDFS follows master-slave architecture.

Figure: What is Hadoop – HDFS

In HDFS, Namenode is the master node and Datanodes are the slaves. Namenode contains the metadata about the data stored in Data nodes, such as which data block is stored in which data node, where are the replications of the data block kept etc. The actual data is stored in Data Nodes.

I also want to add, we actually replicate the data blocks present in Data Nodes, and the default replication factor is 3. Since we are using commodity hardware and we know the failure rate of these hardwares are pretty high, so if one of the DataNodes fails, HDFS will still have the copy of those lost data blocks. You can also configure replication factor based on your requirements. You can go through HDFS tutorial to know HDFS in detail.  

Hadoop-as-a-Solution

Let’s understand how Hadoop provided the solution to the Big Data problems that we just discussed.

Figure: What is Hadoop – Hadoop-as-a-Solution

The first problem is storing Big data.

HDFS provides a distributed way to store Big data. Your data is stored in blocks across the DataNodes and you can specify the size of blocks. Basically, if you have 512MB of data and you have configured HDFS such that, it will create 128 MB of data blocks. So HDFS will divide data into 4 blocks as 512/128=4 and store it across different DataNodes, it will also replicate the data blocks on different DataNodes. Now, as we are using commodity hardware, hence storing is not a challenge.

It also solves the scaling problem. It focuses on horizontal scaling instead of vertical scaling. You can always add some extra data nodes to HDFS cluster as and when required, instead of scaling up the resources of your DataNodes. Let me summarize it for you basically for storing 1 TB of data, you don’t need a 1TB system. You can instead do it on multiple 128GB systems or even less.

Next problem was storing the variety of data.

With HDFS you can store all kinds of data whether it is structured, semi-structured or unstructured. Since in HDFS, there is no pre-dumping schema validation. And it also follows write once and read many model. Due to this, you can just write the data once and you can read it multiple times for finding insights.

Third challenge was accessing & processing the data faster.

Yes, this is one of the major challenges with Big Data. In order to solve it, we move processing to data and not data to processing. What does it mean? Instead of moving data to the master node and then processing it. In MapReduce, the processing logic is sent to the various slave nodes & then data is processed parallely across different slave nodes. Then the processed results are sent to the master node where the results is merged and the response is sent back to the client.  You can get a better understanding with the Data Engineering course.

In YARN architecture, we have ResourceManager and NodeManager. ResourceManager might or might not be configured on the same machine as NameNode. But, NodeManagers should be configured on the same machine where DataNodes are present.

YARN

YARN performs all your processing activities by allocating resources and scheduling tasks.

Figure: What is Hadoop – YARN

It has two major components, i.e. ResourceManager and NodeManager.

ResourceManager is again a master node. It receives the processing requests and then passes the parts of requests to corresponding NodeManagers accordingly, where the actual processing takes place. NodeManagers are installed on every DataNode. It is responsible for the execution of the task on every single DataNode.

I hope now you are clear with What is Hadoop and its major components. Let us move ahead and understand when to use and when not to use Hadoop. 

Where is Hadoop used? 

Hadoop is used for:

• Search – Yahoo, Amazon, Zvents
• Log processing – Facebook, Yahoo
• Data Warehouse – Facebook, AOL
• Video and Image Analysis – New York Times, Eyealike

Till now, we have seen how Hadoop has made Big Data handling possible. But there are some scenarios where Hadoop implementation is not recommended.

When not to use Hadoop?

Following are some of those scenarios :

• Low Latency data access : Quick access to small parts of data
• Multiple data modification : Hadoop is a better fit only if we are primarily concerned about reading data and not modifying data.
• Lots of small files : Hadoop is suitable for scenarios, where we have few but large files.

After knowing the best suitable use-cases, let us move on and look at a case study where Hadoop has done wonders.

Hadoop-CERN Case Study

The Large Hadron Collider in Switzerland is one of the largest and most powerful machines in the world. It is equipped with around 150 million sensors, producing a petabyte of data every second, and the data is growing continuously.

CERN researches said that this data has been scaling up in terms of amount and complexity, and one of the important task is to serve these scalable requirements. So, they setup a Hadoop cluster. By using Hadoop, they limited their cost in hardware and complexity in maintenance.

They integrated Oracle & Hadoop and they got advantages of integrating. Oracle, optimized their Online Transactional System & Hadoop provided them scalable distributed data processing platform. They designed a hybrid system, and first they moved data from Oracle to Hadoop. Then, they executed query over Hadoop data from Oracle using Oracle APIs. They also used Hadoop data formats like Avro & Parquet for high performance analytics without need of changing the end-user apps connecting to Oracle.

The main Hadoop components they are using at the CERN-IT Hadoop service:

You can learn about each of these tool in Hadoop ecosystem blog. 

Techniques for integrating Oracle and Hadoop:

• Export data from Oracle to HDFS

Sqoop was good enough for most cases and they also adopted some of the other possible options like custom ingestion, Oracle DataPump, streaming etc.

• Query Hadoop from Oracle

They accessed tables in Hadoop engines using DB links in Oracle. That also build hybrid views by transparently combining data in Oracle and Hadoop.

• Use Hadoop frameworks to process data in Oracle DBs

They used Hadoop engines (like Impala, Spark) to process data exported from Oracle and then read that data in a RDBMS directly from Spark SQL with JDBC.

Offloading from Oracle to Hadoop

Step1: Offload data to Hadoop

Step2: Offload queries to Hadoop

Step 3: Access Hadoop from an Oracle query

• Query Apache Hive/Impala tables from Oracle using a database link

create database link my_hadoop using 'impala-gateway';

select * from big_table@my_hadoop where col1= :val1;

• Query offloaded via ODBC gateway to Impala (or Hive)

Example of creating hybrid view on oracle

create view hybrid_view as

          select * from online_table where date > '2016-10-01'

          union all

&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; select * from archive_table@hadoop where date <= '2016-10-01'

Based on CERN case study, we can concludes that:

• Hadoop is scalable and excellent for Big Data analytics
• Oracle is proven for concurrent transactional workloads
• Solutions are available to integrate Oracle and Hadoop
• There is a great value in using hybrid systems (Oracle + Hadoop):
  • Oracle APIs for legacy applications and OLTP workloads
  • Scalability on commodity Hardware for analytic workloads

I hope this blog was informative and added value to your knowledge. In our next blog of Hadoop Tutorial Series, i.e. Hadoop Tutorial, we will discuss about Hadoop in more detail and understand task of HDFS & YARN components in detail.

Now that you have understood What is Hadoop, check out the Hadoop training in Delhi by Edureka, a trusted online learning company with a network of more than 250,000 satisfied learners spread across the globe. The Edureka’s Big Data Engineering Course helps learners become expert in HDFS, Yarn, MapReduce, Pig, Hive, HBase, Oozie, Flume and Sqoop using real-time use cases on Retail, Social Media, Aviation, Tourism, Finance domain.

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