Azure SQL (PaaS) Database or SQL Server on Azure VMs (IaaS)

Azure has two options for hosting SQL Server workloads in Microsoft Azure:

  • Azure SQL Database: A SQL database native to the cloud, also known as a platform as a service (PaaS) database or a database as a service (DBaaS) that is optimized for software-as-a-service (SaaS) app development. It offers compatibility with the majority of SQL Server features. For more information on PaaS, see What is PaaS
  • SQL Server on Azure Virtual Machines: SQL Server installed and hosted in the cloud on Windows Server Virtual Machines (VMs) running on Azure, also known as an infrastructure as a service (IaaS).

Learn how each option fits into the Microsoft data platform and get help matching the right option to your business requirements. Whether you prioritize cost savings or minimal administration ahead of everything else, this article can help you decide which approach delivers against the business requirements you care about most.

Microsoft’s data platform

One of the first things to understand in any discussion of Azure versus on-premises SQL Server databases is that you can use it all. Microsoft’s data platform leverages SQL Server technology and makes it available across physical on-premises machines, private cloud environments, third-party hosted private cloud environments, and public cloud. This enables you to meet unique and diverse business needs through a combination of on-premises and cloud-hosted deployments, while using the same set of server products, development tools, and expertise across these environments.

Cloud SQL Server options: SQL server on IaaS, or SaaS SQL database in the cloud.

As seen in the diagram, each offering can be characterized by the level of administration you have over the infrastructure (on the X axis), and by the degree of cost efficiency achieved by database level consolidation and automation (on the Y axis).

When designing an application, four basic options are available for hosting the SQL Server part of the application:

  • SQL Server on non-virtualized physical machines
  • SQL Server in on-premises virtualized machines (private cloud)
  • SQL Server in Azure Virtual Machine (Microsoft public cloud)
  • Azure SQL Database (Microsoft public cloud)

In the following sections, we will learn about SQL Server in the Microsoft public cloud: Azure SQL Database and SQL Server on Azure VMs. In addition, we will explore common business motivators for determining which option works best for your application.

A closer look at Azure SQL Database and SQL Server on Azure VMs

Azure SQL Database is a relational database-as-a-service (DBaaS) hosted in the Azure cloud that falls into the industry categories of Software-as-a-Service (SaaS) and Platform-as-a-Service (PaaS)SQL database is built on standardized hardware and software that is owned, hosted, and maintained by Microsoft. With SQL Database, you can develop directly on the service using built-in features and functionality. When using SQL Database, you pay-as-you-go with options to scale up or out for greater power with no interruption.

SQL Server on Azure Virtual Machines (VMs) falls into the industry category Infrastructure-as-a-Service (IaaS) and allows you to run SQL Server inside a virtual machine in the cloud. Similar to SQL Database, it is built on standardized hardware that is owned, hosted, and maintained by Microsoft. When using SQL Server on a VM, you can either bring your own SQL Server license or use a pre-licensed SQL Server image from the Azure portal.

In general, these two SQL options are optimized for different purposes:

  • SQL Database is optimized to reduce overall costs to the minimum for provisioning and managing many databases. It reduces ongoing administration costs because you do not have to manage any virtual machines, operating system or database software. This includes upgrades, high availability, and backups. In general, Azure SQL Database can dramatically increase the number of databases managed by a single IT or development resource.
  • SQL Server running on Azure VMs is optimized for extending existing on-premises SQL Server applications to the cloud in a hybrid scenario or deploying an existing application to Azure in a migration or dev/test scenario. An example of the hybrid scenario is keeping secondary database replicas in Azure via use of Azure Virtual Networks. With SQL Server on Azure VMs, you have the full administrative rights over a dedicated SQL Server instance and a cloud-based VM. It is a perfect choice when an organization already has IT resources available to maintain the virtual machines. With SQL Server on VMs, you can build a highly customized system to address your application’s specific performance and availability requirements.

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