Azure SQL Databases: Azure SQL Database is a relational database-as-a service using the Microsoft SQL Server Engine. Azure SQL database is a fast growing service with several features being added each month 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.
- The databases are totally isolated from each other and the SQL server is spun up just for a single database or a group of databases, entirely the preference of the person configuring them.
- As the databases are isolated, names of the databases for each instances can be one standard name that is not specific to instance.
- Azure SQL Databases are just individual databases.
- Scalability of Azure SQL Database – The general scale options for Azure SQL Database are so impressive and remarkable.
- Horizontal and geographical scale, which enables database sharing.
- Service tier scale, which lets you change service tiers on-demand, on a schedule, programmatically
- Readable secondaries – like AlwaysOn, Azure SQL database has native support for readable secondaries
SQL Server on an Azure Virtual Machine: These are basically SQL Server installed and hosted in the cloud on Windows Server Virtual Machines (VMs) running on Azure. These are the best examples of Infrastructure as a service (IaaS).
SQL Server on Azure virtual machines is optimized for migrating existing SQL Server applications. All the versions and editions of SQL Server are available. It offers 100% compatibility with SQL Server, allowing you to host as many databases as needed and executing cross-database transactions. It offers full control on SQL Server and Windows.
- Similar to Standard on Premise SQL Server, with facility able to add databases for multiple instances.
- SQL Server on an Azure Virtual Machine can run as many databases as many we want.
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 Server on Azure Virtual Machines (VMs) falls into the industry category Infrastructure-as-a-Service (IaaS) and allows to run SQL Server inside a Virtual Machine in the cloud.
The following table summarizes the main characteristics of SQL Database and SQL Server on Azure VMs:
|Best for:||Azure SQL Database||SQL Server in an Azure Virtual Machine|
|New cloud-designed applications that have time constraints in development and marketing.||Existing applications that require fast migration to the cloud with minimal changes. Rapid development and test scenarios when you do not want to buy on-premises non-production SQL Server hardware.|
|Teams that need built-in high availability, disaster recovery, and upgrade for the database.||Teams that can configure and manage high availability, disaster recovery, and patching for SQL Server. Some provided automated features dramatically simplify this.|
|Teams that do not want to manage the underlying operating system and configuration settings.||You need a customized environment with full administrative rights.|
|Databases of up to 1 TB, or larger databases that can be horizontally or vertically partitioned using a scale-out pattern.||SQL Server instances with up to 64 TB of storage. The instance can support as many databases as needed.|
|Building Software-as-a-Service (SaaS) applications.||Migrating and building enterprise and hybrid applications.|
|Resources:||You do not want to employ IT resources for configuration and management of the underlying infrastructure, but want to focus on the application layer.||You have some IT resources for configuration and management. Some provided automated features dramatically simplify this.|
|Total cost of ownership:||Eliminates hardware costs and reduces administrative costs.||Eliminates hardware costs.|
|Business continuity:||In addition to built-in fault tolerance infrastructure capabilities, Azure SQL Database provides features, such as automated backups, Point-In-Time Restore, geo-restore, and active geo-replication to increase business continuity. For more information, see SQL Database business continuity overview.||SQL Server on Azure VMs lets you set up a high availability and disaster recovery solution for your database’s specific needs. Therefore, you can have a system that is highly optimized for your application. You can test and run failovers by yourself when needed. For more information, see High Availability and Disaster Recovery for SQL Server on Azure Virtual Machines.|
|Hybrid cloud:||Your on-premises application can access data in Azure SQL Database.||With SQL Server on Azure VMs, you can have applications that run partly in the cloud and partly on-premises. For example, you can extend your on-premises network and Active Directory Domain to the cloud via Azure Virtual Network. In addition, you can store on-premises data files in Azure Storage using SQL Server Data Files in Azure. For more information, see Introduction to SQL Server 2014 Hybrid Cloud.|
|Supports SQL Server transactional replication as a subscriber to replicate data.||Fully supports SQL Server transactional replication, AlwaysOn Availability Groups, Integration Services, and Log Shipping to replicate data. Also, traditional SQL Server backups are fully supported|
Reference: SQL Database PasS Vs SQL Server Iaas