Microsoft Azure virtual machines (VMs) with SQL Server can help lower the cost of a high availability and disaster recovery (HADR) database solution. Most SQL Server HADR solutions are supported in Azure virtual machines, both as Azure-only and as hybrid solutions. In an Azure-only solution, the entire HADR system runs in Azure. In a hybrid configuration, part of the solution runs in Azure and the other part runs on-premises in your organization. The flexibility of the Azure environment enables you to move partially or completely to Azure to satisfy the budget and HADR requirements of your SQL Server database systems.
It is up to you to ensure that your database system possesses the HADR capabilities that the service-level agreement (SLA) requires. The fact that Azure provides high availability mechanisms, such as service healing for cloud services and failure recovery detection for Virtual Machines, does not itself guarantee you can meet the desired SLA. These mechanisms protect the high availability of the VMs but not the high availability of SQL Server running inside the VMs. It is possible for the SQL Server instance to fail while the VM is online and healthy. Moreover, even the high availability mechanisms provided by Azure allow for downtime of the VMs due to events such as recovery from software or hardware failures and operating system upgrades.