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Azure Virtual Machines is one of the central features of Azure’s IaaS capabilities, together with Azure Virtual Networks. Azure Virtual Machines supports the deployment of Windows or Linux virtual machines (VMs) in a Microsoft Azure datacenter. You have total control over the configuration of the VM. You are responsible for all server software installation, configuration, and maintenance and for operating system patches.

There are two primary differences between Azure’s PaaS and IaaS compute features: persistence and control. Azure App Service and Web Apps,” PaaS features such as Cloud Services (that is, web and worker roles) and App Services are managed primarily by the Azure platform, allowing you to focus on creating the application and not managing the server infrastructure. With an Azure Virtual Machines VM, you are responsible for nearly all aspects of the VM.

Azure Virtual Machines supports two types of durable (or persistent) disks: OS disks and data disks. An OS disk is required, and data disks are optional. The durability for the disks is provided by Azure Storage. More details on these disks will be provided later in this chapter, but for now understand the OS disk is where the operating system resides (Windows or Linux), and the data disk is where you can store other things, such as application data, images, and so on. By contrast, Azure PaaS cloud services use ephemeral disks attached to the physical host—the data on which can be lost in the event of failure of the physical host.

Because of the level of control afforded to the user and the use of durable disks, VMs are ideal for a wide range of server workloads that do not fit into a PaaS model. Server workloads such as database servers (SQL Server, Oracle, MongoDB, and so on), Windows Server Active Directory, Microsoft SharePoint, and many more become possible to run on the Microsoft Azure platform. If desired, users can move such workloads from an on-premises datacenter to one or more Azure regions, a process often called lift and shift.

Source of Information : Microsoft Azure Essentials Fundamentals of Azure Second Edition