What is Data Warehouse?

A data warehouse is a form of inventory or repository designed explicitly for fast query and analysis of data. It is typically used to support business intelligence activities, such as reporting and analytics.

A data warehouse typically stores large amounts of historical data, often from a variety of sources, such as transactional databases, log files, and external data sources. The data is structured in a specific way to optimize query performance and facilitate analysis. This typically involves organizing the data into a dimensional model, with facts and dimensions, and pre-calculating summary data to enable fast querying.

A data warehouse is designed to support efficient querying and analysis of data rather than the high-speed transaction processing of a transactional database. As a result, it is often updated on a regular basis, with new data added in batch loads, rather than in real time.

Tiers make up a data warehouse architecture. The front-end client, which represents the top tier, uses reporting, analysis, and data mining tools to provide results. The analytics engine, which is used to access and analyze the data, is part of the middle layer. The database server, which loads and stores data, is the lowest tier of the architecture. Data is kept in two separate ways:

1) Often used data is kept in extremely quick storage drives (like SSD drives)

2) Rarely accessed data is kept in an affordable object store, like Amazon S3

Data warehouses are essential for businesses to understand and analyze their data and can provide insights into customer behaviour, sales trends, and other critical business metrics. They are often used with business intelligence tools, such as dashboards and reporting software, to enable data-driven decision making.