Hadoop for Beginners (7): HDFS Data Read and Write Flow
Last time we could already operate HDFS from code, but what actually happens inside the Hadoop cluster? This post gives a quick overview of how HDFS reads and writes data.
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Last time we could already operate HDFS from code, but what actually happens inside the Hadoop cluster? This post gives a quick overview of how HDFS reads and writes data.

Last post covered operating HDFS with shell commands, but in practice we can't keep doing everything by hand — we need automation through code. This post gets you familiar with controlling files in HDFS from Java.

HDFS stands for Hadoop Distributed File System. It is a highly fault-tolerant system designed for deployment on cheap commodity machines. It delivers high-throughput data access, which makes it a great fit for applications over very large data sets.

Last time we tried installing a pseudo-distributed setup, but what you actually use in production is a distributed cluster — that's the real point. This post builds a minimal Hadoop cluster on three nodes to experience a fully distributed environment.

Since this is a beginner course and many people's machines can't handle a real cluster, let's start with Hadoop's single-node mode so you can run simple operations with Hadoop MapReduce and HDFS. This section is basically a Hello World for Hadoop — pulling the mystery off it.

Before we can start our Hadoop journey we need to know how to install it. Later we'll experiment and learn across multiple Hadoop nodes; this post walks through the installation, which is quite simple.

Newer DBeaver versions no longer support ODBC connections, probably because the JDBC-ODBC bridge was removed from Java 8. So the old tutorials telling you to use ODBC no longer work. Here's the correct way to connect DBeaver to DaMeng.

MariaDB/MySQL is case-sensitive on Linux, so any mismatch in capitalization between your table or column names and your SQL throws errors. That's why we usually turn case sensitivity off first.

The previous big chapter covered the concept of a big data warehouse and how to think about building one. Now we start turning those ideas into reality. The foundation carrying all of it is the collection of big data components in the Hadoop ecosystem, which gradually becomes our data warehouse and platform.

Last post covered fact tables, dimension tables, the star schema and the snowflake schema. Beyond those there's more industry jargon to learn. This post explains the big data slang: full tables, incremental tables, zipper tables, transaction tables, and snapshot tables. Some of it may not click yet — it will once you work with Hive — so take this as foundational knowledge.
