Microsoft sees four fundamental requirements for any cloud computing offering. First it must have the ability to scale as customer demand requires. Second, it must provide automated service management, delivering more than just disk space and processors; it must have but the to seamlessly failover scale up scaled down and optimize management of the applications and services it hosts. Third must be highly available, with the highest level of reliability as well as redundancy and fail-over. Finally a must for multi-tenancy, concurrent hosting of multiple customers to optimize utilization and control costs.Beyond these fundamental requirements, there are also a number of considerations -- variables -- for cloud computing platforms. They may be located on premises (within IT data center) or remotely hosted by the provider and accessed over the Internet. The infrastructure they provide may support a single type of technology, or have the ability to host heterogeneous, interoperable technologies. The business model costs might be optimized for operating expenses or towards capital investment. The hardware and networking resources might be leased or owned. And the management of the IT systems might be self directed by the business or performed by a third party, perhaps cloud computing platform provider.
From the customer’s perspective, SQL Azure provides logical databases for application data storage. In reality, each customer’s data is actually stored in multiple SQL Server databases, which are distributed across multiple physical servers. Many customers may share the same physical database, but the data is presented to the customer through a logical database that abstracts the physical storage architecture and uses automatic load balancing and connection routing to access the distributed data. Security and isolation is managed automatically.The key impact of this model for the customer is a move from managing physical servers to focus on logical management of data storage through policies.