Horizontally scaling SQL Server, distributing the database with sharding
Is there material on how?


Yes. You can read about it at https://msdn.microsoft.com/en-us/library/dn589797.aspx


  Is the process as tough as it seems?


Sort of. It is time consuming in that it requires careful planning in advance on how you want to structure the data, but if you're doing something with a massive database, I've personally been very pleased with the performance enhancement.