More information: Google cloud databases
Microsoft uses its SQL Server technology to provide a relational database, allowing customers to either access a SQL database on its cloud, or hosted SQL server instances on virtual machines. Microsoft also emphasizes hybrid databases that combine data both on a customer's premise and with the Azure cloud through SQL Data Sync. Microsoft has a cloud-hosted NoSQL database service named Tables as well, while Blobs (binary large object storage), are optimized for media files such as audio and video.
More information: Microsoft Azure
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In the NoSQL world, there are a variety of database platforms to choose from, including MongoDB. MongoLab gives users access to MongoDB on a variety of major cloud providers, including AWS, Azure and Joyent. Like other gateway-type services, MongoLab also integrates with various platform as a service (PaaS) tools at the application tier. MongoLab run on either shared or dedicated environments, with the latter being slightly more expensive.
More information: MongoLab
Rackspace's database comes in either a cloud or managed hosted offering via Cloud Databases, which is the name of its product. Rackspace emphasizes the container-based virtualization of its Cloud Databases, which it says allow for higher performance of the database service compared to if it was run entirely on virtualized infrastructure. Cloud Databases also incorporates a SAN storage network and it's based on an OpenStack platform. This month, Rackspace announced a NoSQL database in its cloud from provider Cloudant.
More information: Rackspace Cloud Databases
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