• Azure Fabric Controller get commands from RDFE.
• The RDFE acts as kind of router for request and traffic to and from the load balancer and Fabric Controller.
• When you log in to Azure portal and ask for a new service say for example “Web Role” instance, the portal send this request first to RDFE.
• The RDFE asks the Fabric Controller for the same, based on the parameters you set and your location, proximity etc.
• The Fabric Controller scans the available nodes in the racks and looks for two nodes that do not share a Fault Domain.
• This could be two racks next to each other as Fabric Controller considers network proximity and available connectivity as Factors in optimizing performance.
• Azure is unlikely to pick nodes in two different facilities unless necessary or specified.
• Once Fabric Controller found its nodes, then puts the role-defining files at the host.
• The host OS creates the requested Virtual machines and three virtual Hard Drives, a stock VHD (D :\) for the OS Image, a resource VHD(C :\) for user temporary files (next available drive letter) and a Role VHD for role specific files.
• The load balancers do nothing until the instance receives its first external HTTP Communication.
• Only then is the instance routed to an external endpoint and live to network.