Let's start with a single VM and take a look at the first diagram:

In the preceding diagram, you can see the simplest representation of an Azure VM. An Azure VM consists of an OS disk (which contains the operating system of your VM) and the optional data disks (which serves as a store for the data of your applications). Both disk types are Virtual Hardware Disks (VHD) and thus physical files, which are stored as blob in a storage account of your Azure account. The storage of the disks is persistent.

Theoretically, we now have everything together. In reality, however, numerous other resources are still necessary. Some resources are mandatory, other resources can be used as an option.

Let's take a look at the second diagram:

In the preceding diagram, you can now see a complex representation of an Azure VM. Let's look at it once more in detail:

Mandatory resources of an Azure VM are the following:

• Resource group: A resource group is a container that holds all related resources
• Virtual Network (VNet) and VNet subnets: Every VM in Azure is hosted into a VNet that is supplementarily divided into VNet subnets
• VM storage account: The VM storage account is the place where you store the VHDs of the OS disk or the data disks
• Network interface (NIC): The NIC enables the VM to communicate with the VNet

Optional resources of an Azure VM are the following:

• VM Agent: The VM Agent is a lightweight process that manages the VM interaction with the Azure Fabric Controller (this is the main control of the Azure platform). However, the primary role of a VM Agent is to enable and execute Azure VM extensions. The VM Agent is installed by default on any VM deployed from an Azure Gallery image. For VMs based on a custom image, a subsequent manual installation is required.
• VM extensions: VM extensions are small applications that provide post-deployment configuration and automation tasks on Azure VMs. The following VM extensions are currently available for the following:
  • VM Custom Script Extension: The Custom Script Extension allows any PowerShell script to be run on a virtual machine.
  • VM PowerShell Desired State Configuration (DSC) extension: The PowerShell DSC extension allows us to apply PowerShell DSC to a virtual machine.
  • Operations Management Suite (OMS) Agent extension: The OMS Agent extensions extends your Azure infrastructure to an OMS workspace.
  • Azure Log Collector Extension: The Azure Log Collector enables a log collector to your Azure infrastructure. You can use the extension to perform one-time collection of logs from one or more VMs and transfer the collected files to an Azure Storage account.
  • Azure Diagnostics extensions: The Azure Diagnostics extension enables Azure Diagnostics to your Azure infrastructure.
  • Microsoft Monitoring Agent VM extension (for Windows only): The Microsoft Monitoring Agent VM extension enables Log Analytics to your Azure infrastructure. If you run a Linux VM, use the OMS Agent extension for Linux instead.
  • VM extension for Datadog: The VM extension for Datadog extends your Azure infrastructure to a Datadog environment (extended monitoring).
  • VM extension for Chef: The VM extension for Chef extends your Azure infrastructure to a Chef environment (extended monitoring and configuration).
  • Public IP address: A public IP address is needed to communicate with the VM-for example over the Remote Desktop Service (RDP).

Not shown in the diagram is the following resource (also optional):

• Network Security Group (NSG): An NSG is used to allow or deny network traffic. You can associate an NSG with an individual NIC or with a VNet subnet. If you associate it with a VNet subnet, the NSG rules apply to all VMs in that subnet.