We can put SQL Server architecture in 3 main categories…

    1. Protocol Layer
    2. Storage Layer
    3. OS Layer 

1. Protocol Layer
      Connection Protocol
      Query Processing

2. Storage Layer
     Lock Manager
     Transaction Manager
     File Manager

     Buffer Manager 

3. OS Layer
    Scheduler Manager
    Memory Manager
    Resource Manager
    Lazy Writer
    Deadlock
    IO Manager.