SQL Azure currently supports 1 GB and 10 GB databases. If you want to store larger amounts of data in SQL Azure you can divide your tables across multiple SQL Azure databases. “This article will discuss how to use a middle layer to join two tables on different SQL Azure databases using LINQ. This technique vertically partitions your data in SQL Azure. In this version of vertically partitioning for SQL Azure we’re dividing all the tables in the schema across two or more SQL Azure databases. In choosing which tables to group together on a single database you need to understand how large each of your tables are and their potential future growth – the goal is to evenly distribute the tables so that each database is the same size. There’s also a performance gain to be obtained from partitioning your database. Since SQL Azure spreads your databases across different physical machines, you can get more CPU and RAM resources by partitioning your workload. For example, if you partition your database across 10 - 1 GB SQL Azure databases you get 10X the CPU and memory resources,” writes Microsoft.
More Info: Vertical Partitioning in SQL Azure: Part 1