NoSQL DEFINITION:Next Generation Databases mostly addressing some of the points: being non-relational, distributed, open-source and horizontal scalable.
Load scalability: The ability for a distributed system to easily expand and contract its resource pool to accommodate heavier or lighter loads. Alternatively, the ease with which a system or component can be modified, added, or removed, to accommodate changing load.
Scale horizontally (scale out)
To scale horizontally (or scale out) means to add more nodes to a system, such as adding a new computer to a distributed software application. An example might be scaling out from one web server system to three.
Windows Azure Table provides scalable, available, and durable structured storage in the form of tables. The tables contain entities, and the entities contain properties. The tables are scalable to billions of entities and terabytes of data, and may be partitioned across thousands of servers.
Windows Azure Storage provides durable, scalable, available, and performance-efficient storage services for the cloud,
Windows Azure Blob provides a simple interface for storing named files along with metadata for a file.
As Google has demonstrated, a pure SN system can scale almost infinitely simply by adding nodes in the form of inexpensive computers, since there is no single bottleneck to slow the system down.
Shared Disk Architectures are write limited should they require locks that must be coordinated across the cluster.
Shared Nothing Architectures are write limited should they require a distributed two phase commit.
Reads in Shared Disk Architectures can suffer from resource starvation issues and less efficient caching as the cluster scales. Shared Nothing Architectures have the potential for far more scale but this can be hampered by queries that must hit all machines. Query speed can also be affected if non-result (intermediary) data sets must be shipped cross-machine.