Cloud database
A cloud database is a database that typically runs on a cloud computing platform, and access to the database is provided as-a-service.
Database services take care of scalability and high availability of the database. Database services make the underlying software-stack transparent to the user.
Deployment models
There are two primary methods to run a database in a cloud:; Virtual machine image: Cloud platforms allow users to purchase virtual-machine instances for a limited time, and one can run a database on such virtual machines. Users can either upload their own machine image with a database installed on it, or use ready-made machine images that already include an optimized installation of a database.
; Database-as-a-service : With a database as a service model, application owners do not have to install and maintain the database themselves. Instead, the database service provider takes responsibility for installing and maintaining the database, and application owners are charged according to their usage of the service. This is a type of Saas - Software as a Service.
Architecture and common characteristics
- Most database services offer web-based consoles, which the end user can use to provision and configure database instances.
- Database services consist of a database-manager component, which controls the underlying database instances using a service API. The service API is exposed to the end user, and permits users to perform maintenance and scaling operations on their database instances.
- Underlying software-stack stack typically includes the operating system, the database and third-party software used to manage the database. The service provider is responsible for installing, patching and updating the underlying software stack and ensuring the overall health and performance of the database.
- Scalability features differ between vendorssome offer auto-scaling, others enable the user to scale up using an API, but do not scale automatically.
- There is typically a commitment for a certain level of high availability. This is achieved by replicating data and failing instances over to other database instances..
Data model
Modern relational databases have shown poor performance on data-intensive systems, therefore, the idea of NoSQL has been utilized within database management systems for cloud based systems. Within NoSQL implemented storage, there are no requirements for fixed table schemas, and the use of join operations is avoided. "The NoSQL databases have proven to provide efficient horizontal scalability, good performance, and ease of assembly into cloud applications." Data models relying on simplified relay algorithms have also been employed in data-intensive cloud mapping applications unique to virtual frameworks.
It is also important to differentiate between cloud databases which are relational as opposed to non-relational or NoSQL:
; SQL databases: are one type of database which can run in the cloud, either in a virtual machine or as a service, depending on the vendor. While SQL databases are easily vertically scalable, horizontal scalability poses a challenge, that cloud database services based on SQL have started to address.
; NoSQL databases: are another type of database which can run in the cloud. NoSQL databases are built to service heavy read/write loads and can scale up and down easily, and therefore they are more natively suited to running in the cloud. However, most contemporary applications are built around an SQL data model, so working with NoSQL databases often requires a complete rewrite of application code.
Vendors
The following table lists notable database vendors with a cloud database offering, classified by their deployment model – machine image vs. database as a service – and data model, SQL vs. NoSQL.| Virtual Machine Deployment | Database as a Service | |
| SQL Data Model | ||
| NoSQL Data Model |