ASP.NET identity is an extensible system that enables you to create your own storage provider and use it i your application without re-working your application. By default, ASP.NET identity system stores user information in SQL Server database, and uses Entity Framework Code First to create a database. In many applications, this approach works fine. But you may prefer to use a different type of persistence mechanism, like Windows Azure Table Storage, or you may already have a database table with very different structure than the default one.
You can write a customized provider for your storage mechanism and plug that provider to your application.
Read the rest of the tutorial here: Â http://www.asp.net/identity/overview/extensibility/overview-of-custom-storage-providers-for-aspnet-identity