{"id":2182,"date":"2025-06-06T05:28:24","date_gmt":"2025-06-06T05:28:24","guid":{"rendered":"https:\/\/serverhub.com\/kb\/?p=2182"},"modified":"2025-06-09T12:35:37","modified_gmt":"2025-06-09T12:35:37","slug":"introduction-what-is-apache-hadoop","status":"publish","type":"post","link":"https:\/\/serverhub.com\/kb\/introduction-what-is-apache-hadoop\/","title":{"rendered":"Introduction: What is Apache Hadoop?"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\"><strong>What is Hadoop<\/strong>?<\/h2>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"819\" height=\"1024\" src=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Blog-Article-1-Post-819x1024.jpg\" alt=\"\" class=\"wp-image-2208\" srcset=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Blog-Article-1-Post-819x1024.jpg 819w, https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Blog-Article-1-Post-240x300.jpg 240w, https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Blog-Article-1-Post-768x960.jpg 768w, https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Blog-Article-1-Post.jpg 1080w\" sizes=\"(max-width: 819px) 100vw, 819px\" \/><\/figure>\n\n\n\n<p>Apache Hadoop is an open-source software framework designed for distributed storage and processing of massive data sets across clusters of computers using simple programming models. It is built to scale from a single server to thousands of machines, each offering local computation and storage.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is Apache Hadoop?<\/strong><\/h2>\n\n\n\n<p>Developed by the Apache Software Foundation, Apache Hadoop was inspired by Google&#8217;s MapReduce and Google File System (GFS) papers. Today, it forms the backbone of many large-scale data processing platforms.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is Hadoop Used For?<\/strong><\/h2>\n\n\n\n<p>Hadoop is used for processing and storing Big Data\u2014data sets that are too large or complex for traditional data-processing software. It is the foundation of most modern big data applications, enabling organizations to manage petabytes of structured, semi-structured, and unstructured data. Some common use cases include:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Log Processing<\/strong><\/li>\n\n\n\n<li><strong>Recommendation Engines<\/strong><\/li>\n\n\n\n<li><strong>Data Warehousing<\/strong><\/li>\n\n\n\n<li><strong>Clickstream Analysis<\/strong><\/li>\n\n\n\n<li><strong>Machine Learning Pipelines<\/strong><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Hadoop Software Architecture<\/strong><\/h2>\n\n\n\n<p>The Hadoop architecture consists of four primary modules:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Hadoop Common:<\/strong> Core utilities and libraries.<\/li>\n\n\n\n<li><strong>HDFS (Hadoop Distributed File System):<\/strong> Storage layer.<\/li>\n\n\n\n<li><strong>YARN (Yet Another Resource Negotiator):<\/strong> Resource management.<\/li>\n\n\n\n<li><strong>MapReduce: <\/strong>Processing engine.<\/li>\n<\/ol>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"600\" height=\"228\" src=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Hadoop-Components.jpg\" alt=\"\" class=\"wp-image-2187\" srcset=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Hadoop-Components.jpg 600w, https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Hadoop-Components-300x114.jpg 300w\" sizes=\"(max-width: 600px) 100vw, 600px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is is Hadoop Distributed File System (HDFS)?<\/strong><\/h2>\n\n\n\n<p><strong>HDFS in Hadoop?<\/strong> HDFS is a <strong>distributed file system in Hadoop<\/strong> designed to store large files reliably. It splits large files into blocks (typically 128MB or 256MB) and distributes them across nodes in a Hadoop cluster.<\/p>\n\n\n\n<p><strong>HDFS Data Flow Simplified:<\/strong><br><strong>A) Write Operation<\/strong> <strong>Steps:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Client contacts the NameNode to create a file.<\/li>\n\n\n\n<li>NameNode splits the file into blocks and selects DataNodes to store them.<\/li>\n\n\n\n<li>Client writes each block directly to the first DataNode.<\/li>\n\n\n\n<li>That DataNode forwards the block to a second DataNode, which then forwards it to a third (this is called pipelined replication)<\/li>\n<\/ol>\n\n\n\n<p><strong>B) Read Operation Procedures Steps:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Client requests file from NameNode.<\/li>\n\n\n\n<li>NameNode returns a list of DataNodes holding each block.<\/li>\n\n\n\n<li>Client reads blocks directly from the closest or fastest DataNodes.<\/li>\n<\/ol>\n\n\n\n<p><strong>C) Built-in Fault Tolerance Steps:<\/strong><\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Each block is replicated (usually 3 copies).<\/li>\n\n\n\n<li>If a DataNode fails, HDFS reads from another replica.<\/li>\n\n\n\n<li>Lost replicas are automatically restored by the NameNode.<\/li>\n<\/ol>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"624\" height=\"416\" src=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/HDFS-Data-Flow.jpg\" alt=\"\" class=\"wp-image-2190\" srcset=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/HDFS-Data-Flow.jpg 624w, https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/HDFS-Data-Flow-300x200.jpg 300w\" sizes=\"(max-width: 624px) 100vw, 624px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is a Hadoop Cluster?<\/strong><\/h2>\n\n\n\n<p>A Hadoop cluster is a collection of computers (nodes) networked together to work as a single system. It includes:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Master Node:<\/strong> NameNode (manages HDFS metadata) and ResourceManager (for YARN).<\/li>\n\n\n\n<li><strong>Nodes:<\/strong> DataNode (stores actual data) and NodeManager (runs tasks).<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is is Hadoop MapReduce?<\/strong><\/h2>\n\n\n\n<p>MapReduce is a core component of the Hadoop ecosystem used for processing large data sets. It involves two primary functions:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Mapper:<\/strong> Breaks a task into smaller sub-tasks.<\/li>\n\n\n\n<li><strong>Reducer:<\/strong> Aggregates the results.<\/li>\n<\/ul>\n\n\n\n<p><strong>What does Hadoop&#8217;s map procedure from its MapReduce program do?<\/strong> It filters and sorts of data into key-value pairs for further processing by the reducer.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is Hive in Hadoop?<\/strong><\/h2>\n\n\n\n<p><strong>What is Hive and Hadoop?<\/strong> Hive is a data warehouse infrastructure built on top of Hadoop. It allows users to query data using HiveQL, a SQL-like language.<\/p>\n\n\n\n<p><strong>What is Hive in Hadoop?<\/strong> Hive simplifies querying, summarizing, and analyzing large-scale data. It translates HiveQL into MapReduce jobs under the hood.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is Big Data and Hadoop?<\/strong><\/h2>\n\n\n\n<p><strong>What is Big Data Hadoop? <\/strong>It refers to using the Hadoop ecosystem to manage big data. The framework is built to handle the 3Vs of big data:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Volume:<\/strong> Terabytes to petabytes.<\/li>\n\n\n\n<li><strong>Velocity:<\/strong> Real-time or near-real-time.<\/li>\n\n\n\n<li><strong>Variety:<\/strong> Structured, semi-structured, and unstructured.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>How Does Hadoop Work?<\/strong><\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Data Ingestion:<\/strong> Using tools like <strong>Flume <\/strong>or <strong>Sqoop<\/strong>.<\/li>\n\n\n\n<li><strong>Storage:<\/strong> Data is split and distributed using HDFS.<\/li>\n\n\n\n<li><strong>Processing:<\/strong> Tasks are scheduled using YARN and executed using <strong>MapReduce<\/strong>, <strong>Hadoop Spark<\/strong>, or <strong>Tez<\/strong>.<\/li>\n\n\n\n<li><strong>Querying:<\/strong> Via Hive, Pig, or Spark SQL.<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>What is Hadoop Spark?<\/strong><\/h2>\n\n\n\n<p><strong>Hadoop Spark<\/strong>, or more precisely <strong>Apache Spark<\/strong>, is a fast, in-memory data processing engine. While Hadoop uses disk-based MapReduce, Spark leverages in-memory processing, making it much faster for iterative algorithms like those in<\/p>\n\n\n\n<p><strong>Hadoop vs Spark:<\/strong> Spark is more efficient for real-time and batch processing, whereas Hadoop MapReduce is more disk-reliant but stable for batch jobs.<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"624\" height=\"351\" src=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Hadoop-vs.-Spark.jpg\" alt=\"\" class=\"wp-image-2195\" srcset=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Hadoop-vs.-Spark.jpg 624w, https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Hadoop-vs.-Spark-300x169.jpg 300w\" sizes=\"(max-width: 624px) 100vw, 624px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Hadoop Spark SQL and Architecture<\/strong><\/h2>\n\n\n\n<p>Hadoop Spark SQL allows for querying data using SQL while leveraging Spark&#8217;s in-memory computation. Its architecture integrates with Hadoop through YARN and can be read from HDFS, Hive, and even external sources.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Is Hadoop a Database?<\/strong><\/h2>\n\n\n\n<p>No, <strong>Hadoop is not a database<\/strong>. It\u2019s a framework for distributed computing. Unlike traditional databases, Hadoop doesn\u2019t support real-time querying or indexing by default. However, tools like Hive simulate database behavior on top of Hadoop.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>How to Use -copyFromLocal in Hadoop?<\/strong><\/h2>\n\n\n\n<p>The command <strong>hadoop fs -copyFromLocal &lt;source&gt; &lt;destination&gt;<\/strong> is used to copy files from the local file system to HDFS. The following is an example command:<br><strong>hadoop fs -copyFromLocal \/home\/user\/data.csv \/user\/hadoop\/data.csv<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Hadoop Ecosystems Components<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>HDFS<\/strong> \u2013 Distributed storage<\/li>\n\n\n\n<li><strong>MapReduce<\/strong> \u2013 Processing engine<\/li>\n\n\n\n<li><strong>Hive<\/strong> \u2013 Data warehouse interface<\/li>\n\n\n\n<li><strong>Pig<\/strong> \u2013 Data flow language<\/li>\n\n\n\n<li><strong>Spark<\/strong> \u2013 In-memory processing<\/li>\n\n\n\n<li><strong>Oozie<\/strong> \u2013 Workflow scheduler<\/li>\n\n\n\n<li><strong>Flume<\/strong> \u2013 Log data ingestion<\/li>\n\n\n\n<li><strong>Sqoop<\/strong> \u2013 Import\/export from RDBMS<\/li>\n\n\n\n<li><strong>YARN<\/strong> \u2013 Resource management<\/li>\n<\/ul>\n\n\n\n<figure class=\"wp-block-image size-full\"><img decoding=\"async\" width=\"624\" height=\"416\" src=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Haddop-Ecosystem-Components.jpg\" alt=\"\" class=\"wp-image-2198\" srcset=\"https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Haddop-Ecosystem-Components.jpg 624w, https:\/\/serverhub.com\/kb\/wp-content\/uploads\/2025\/06\/Haddop-Ecosystem-Components-300x200.jpg 300w\" sizes=\"(max-width: 624px) 100vw, 624px\" \/><\/figure>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>How to Learn Hadoop?<\/strong><\/h2>\n\n\n\n<p>If you&#8217;re wondering how I can learn Hadoop, there are several great starting points:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>OMSA Learning Hadoop Spark:<\/strong> A practical course for beginners.<\/li>\n\n\n\n<li><strong>Cloudera Hadoop Tutorials:<\/strong> Enterprise-level training.<\/li>\n\n\n\n<li><strong>Apache Foundation Hadoop Docs:<\/strong> Official documentation.<\/li>\n\n\n\n<li><strong>YouTube Tutorials:<\/strong> Visual and hands-on learning.<\/li>\n\n\n\n<li><strong>Books:<\/strong> \u201cHadoop: The Definitive Guide\u201d by Tom White.<\/li>\n<\/ul>\n\n\n\n<p>You can start with a <strong>big data Hadoop and Spark project for absolute beginners Hadoop<\/strong> to get hands-on experience.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Installing Hadoop<\/strong><\/h2>\n\n\n\n<p>The steps for <strong>Hadoop software installation<\/strong>:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Download Hadoop from <a href=\"https:\/\/hadoop.apache.org\/releases.html\" title=\"https:\/\/hadoop.apache.org\/releases.html\">https:\/\/hadoop.apache.org\/releases.html<\/a><\/li>\n\n\n\n<li>Extract and configure <strong>core-site.xml, hdfs-site.xml<\/strong>, and <strong>mapred-site.xml<\/strong>.<\/li>\n\n\n\n<li>Format HDFS with the following command: <strong>hdfs namenode -format<\/strong><\/li>\n\n\n\n<li>Start services using the following command: <strong>start-dfs.sh &amp;&amp; start-yarn.sh<\/strong><\/li>\n<\/ol>\n\n\n\n<ul class=\"wp-block-list\">\n<li>To check <strong>Hadoop versions<\/strong>, use the following commands: <strong>hadoop version<\/strong><\/li>\n<\/ul>\n\n\n\n<p>For Maven integration:<\/p>\n\n\n\n<p><strong>&lt;property&gt;<\/strong><\/p>\n\n\n\n<p>&nbsp; <strong>&lt;name&gt;hadoop.version&lt;\/name&gt;<\/strong><\/p>\n\n\n\n<p>&nbsp; <strong>&lt;value&gt;3.3.1&lt;\/value&gt;<\/strong><\/p>\n\n\n\n<p><strong>&lt;\/property&gt;<\/strong><\/p>\n\n\n\n<p>Use <strong>mvn cli set hadoop<\/strong> version if working on Java or Scala-based apps.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Hadoop on ARM<\/strong><\/h2>\n\n\n\n<p>Hadoop supports ARM architecture, especially with the rise of ARM-based servers and cloud computing. Custom builds are available for ARM64 processors.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Final Thoughts: What Does Hadoop Do?<\/strong><\/h2>\n\n\n\n<p>So, <strong>what does Hadoop do?<\/strong> In essence, Hadoop will allow organizations to:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Store large data sets efficiently.<\/li>\n\n\n\n<li>Process massive data in parallel.<\/li>\n\n\n\n<li>Query data with SQL-like interfaces.<\/li>\n\n\n\n<li>Build scalable big data applications.<\/li>\n<\/ul>\n\n\n\n<p>It is <strong>not a traditional database<\/strong> but rather a distributed computing platform. Hadoop is a cornerstone of the <strong>Big Data revolution<\/strong> and continues to evolve through tools like <strong>Hadoop Spark<\/strong>, <strong>Hive<\/strong>, and <strong>YARN<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Bonus: Hadoop HADOOP_OPTS<\/strong><\/h2>\n\n\n\n<p>Environment variable <strong>HADOOP_OPTS<\/strong> is used to pass custom JVM options to Hadoop processes, e.g., for logging or memory allocation by using the following command:<br><strong>export HADOOP_OPTS=&#8221;-Djava.net.preferIPv4Stack=true&#8221;<\/strong><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>References:<\/strong><\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><a href=\"https:\/\/hadoop.apache.org\/\" title=\"Apache Hadoop\">Apache Hadoop<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/spark.apache.org\/\" title=\"\">Apache Spark\u2122 &#8211; Unified Engine for large-scale data analytics<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/cwiki.apache.org\/confluence\/display\/Hive\/Home\" title=\"\">Home &#8211; Apache Hive &#8211; Apache Software Foundation<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/hadoop.apache.org\/docs\/stable\/hadoop-yarn\/hadoop-yarn-site\/YARN.html\" title=\"Apache Hadoop 3.4.1 \u2013 Apache Hadoop YARN\">Apache Hadoop 3.4.1 \u2013 Apache Hadoop YARN<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/hadoop.apache.org\/docs\/stable\/hadoop-project-dist\/hadoop-hdfs\/HdfsDesign.html\" title=\"\">Apache Hadoop 3.4.1 \u2013 HDFS Architecture<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.omsa.org\/\" title=\"\">Orders &amp; Medals Society of America<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.youtube.com\/user\/Simplilearn\" title=\"Simplilearn - YouTube\">Simplilearn &#8211; YouTube<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/cloud.google.com\/solutions\/data-analytics-and-ai\" title=\"\">Data analytics and AI platform: BigQuery | Google Cloud<\/a><\/li>\n<\/ol>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is Hadoop? Apache Hadoop is an open-source software framework designed for distributed storage and processing of massive data sets across clusters of computers using simple programming models. It is built to scale from a single server to thousands of machines, each offering local computation and storage. What is Apache Hadoop? Developed by the Apache &#8230; <a title=\"Introduction: What is Apache Hadoop?\" class=\"read-more\" href=\"https:\/\/serverhub.com\/kb\/introduction-what-is-apache-hadoop\/\" aria-label=\"More on Introduction: What is Apache Hadoop?\">Read more<\/a><\/p>\n","protected":false},"author":6,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_bbp_topic_count":0,"_bbp_reply_count":0,"_bbp_total_topic_count":0,"_bbp_total_reply_count":0,"_bbp_voice_count":0,"_bbp_anonymous_reply_count":0,"_bbp_topic_count_hidden":0,"_bbp_reply_count_hidden":0,"_bbp_forum_subforum_count":0,"om_disable_all_campaigns":false,"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"_uf_show_specific_survey":0,"_uf_disable_surveys":false,"footnotes":""},"categories":[1],"tags":[167],"class_list":["post-2182","post","type-post","status-publish","format-standard","hentry","category-uncategorized","tag-apachehadoop-bigdata-dataanalytics-serverhub-dedicatedservers-vps"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/posts\/2182","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/comments?post=2182"}],"version-history":[{"count":20,"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/posts\/2182\/revisions"}],"predecessor-version":[{"id":2209,"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/posts\/2182\/revisions\/2209"}],"wp:attachment":[{"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/media?parent=2182"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/categories?post=2182"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/serverhub.com\/kb\/wp-json\/wp\/v2\/tags?post=2182"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}