I consider the data warehouse as the foundation of a business intelligence solution – your single source of truth. As with any good structure if the foundation is not good the structure will come crumbling down. Before we go any further about the importance of a data warehouse in a bi solution lets define it. A data warehouse is a large repository that contains data that is collected from a wide range of sources. These sources of data are usually the business’s transactional systems. The data warehouse is used to guide decision making at all levels and is optimized from read access. Taking the time here to build your warehouse by defining your schemas and tables is crucial to the solution and the business. You do not want to rush through this part by any means. By not designing the data warehouse correctly the project’s cost can increase significantly, cause delays as well as potentially incorrect reporting of the data that is being stored in the warehouse incorrectly. Take your time here to ask the right questions, develop the right solution, review the solution with your team, and then implement and test. You will need to make sure the data warehouse is not only designed right but can also grow and scale as your business’s data needs grow. One thing you do not want to happen is in six months to a year you are getting reports that the system is either slow and/or unresponsive. If one of my clients were asking me about this situation, my first thoughts would be around did the team calculate the right size warehouse or server, did they miss something within the database structure (wrong join, wrong columns were index, etc.). I can not say this enough, the data warehouse is the foundation of the business intelligence solution and it deserves the time to be designed, built, and tested correctly. Like I stated earlier if the foundation is bad then your business intelligence solution will have many issues, if you do not do your due diligence around the building of the data warehouse your solution will have a lot of issues in the future.