What is the difference between software-defined storage and traditional storage?

Take unified storage of sandstone, a software-defined storage product of Shan Yan data, as an example. Traditional storage is mainly based on proprietary hardware, while software-defined storage is mainly based on software, using general hardware products; In terms of scalability, traditional storage is troublesome to expand and its performance is limited, while software-defined storage is simple to expand and its performance is linear. Of course, there are other differences in management and compatibility, so I won't say much here.