Space required by the application

Each application has its own set of requirements, and storage requirements are as necessary as any other requirements.

Serving media files require considerably more resources than a website with few users and not many media files. Knowing precisely what the intended usage of the storage system is permits correct sizing of the solution and prevents situations where storage estimates fall short of what was needed from the beginning.

Make sure you go through what minimum requirements the application developers recommend and understand how it interacts with the storage, as this helps prevent headaches.