SQL Azure Architecture

SQL Azure, which resides in the Microsoft Data Center, provides relational databases to applications with four layers of abstraction.

Four layers of abstraction can be depicted as below:



Client Layer

This layer is closest to the application. SQL Azure connects with client applications with a Tabular Data Stream interface in exactly the same way SQL Server does.

The client layer can range from a managed .NET application to a PHP application. It could be a SilverLight web application or a WCF Data Service. Client layers connect with other layers using a Tabular Data Stream.



The client layer may be in a client data center (on premise) or it may be in the Data Center of the service provider (Cloud).



Service layer performs task of provisioning of database to the user coresponding to the Azure account. This mainly performs:

1. Provisioning of Database to a Azure account
2. Billing of the usage
3. It performs the task of connection routing between client applications from the client layer to the actual physical SQL server in Platform layer.

Platform Layer

Physically SQL Server resides in this layer. There could be many instances of SQL Server.


SQL Azure Fabric manages instance of SQL Server.

Task performed by SQL Azure Fabric

1. It enables automatic failover
2. It does load balancing
3. It does automatic replication between physical servers.
   
   
   

Each instance of SQL Server is individually managed by SQL Azure Fabric.

Management Services performs below tasks,

1. Monitoring health of individual servers.
2. Installing patch up
3. Upgrading services
4. Automated installations

Infrastructure Layer

In this layer IT level administration tasks are performed. Physical hardware and operating systems are administered in this layer.