Azure DevOps Virtual Machine | components

Azure DevOps Virtual Machine | components

Provisioning a virtual machine in Azure involves more components than the virtual machine itself. With the adaptation of ARM, Azure decomposed the virtual machine into a set of services. There is computing, networking, storage, and other peripheral elements. When provisioning the virtual machine (from the portal or template), we should always consider these services as individuals, and then provide their references if necessary.

Here is a high-level decomposition of services which constitute a Virtual Machine in Azure-

Resource group - A resource group functions as a container for a set of resources that share the same lifecycle and management policies. As stated earlier, VM is actually a combination of several services glued together, we need 'a group of resources to contain them in the same basket.

Virtual network - With the ARM deployment model, each virtual machine must be deployed within a virtual network to provide isolation/control over the provisioned infrastructure. Once the virtual network is in place, we need to further divide into a subnet (VLAN concept in the data center) and this is where each virtual machine will be provisioned.

Virtual machine - For IaaS VM was the main construction. Now when you migrate the virtual machine from on-prem, you can directly convert the machines to VHD (Azure only supports VHD, VHDX support is not yet easy).

 Operating System Disk - This is a VHD file supported by Azure storage to provide a persistent operating disk to Azure virtual machines. Due to its persistence, it is immune to the failure of the host machine.

Temporary disk - This is ephemeral storage which is provided to you free of charge by Azure. Any virtual machine when it is created will always be supplied with a temporary disk (drive D: under Windows). This disk is stored in a physical drive on the host machine

Data disks - Like the operating system disk, this is also stored on Azure storage as Page Blob. Unlike the temporary disk, this provides persistent storage for application data.

Public IP - Once provisioned, the VM will get a private IP from the list of available apps in the specified subnet. But this cannot be used for public communication like RDP until you have VPN connectivity in place. To facilitate the same, you can create a public IP and associate it with the aforementioned VM.

NIC- NICs (network interface cards) are essential for any virtual machine provisioned in Azure. It encapsulates all information related to the network and communication.

NSG- NSG (Network Security Groups) are used to control the flow of incoming and outgoing traffic to your virtual machine. It is an extension of the access control lists (ACL) that were used in the classic model.

Diagnostics - Diagnostic logging provides you with appropriate logs that could be used for troubleshooting.

After discussing the main components, let's explore some of the best practices -

1. Use Azure managed disks with virtual machines

When you choose this option, you don't have to worry about placing disks on multiple storage accounts to make sure you meet the scalability limits for storage accounts. It is now Azure's responsibility to do this management for you. - Azure handles this for you.

2. Preventing charges for the Azure virtual machine when not in use

One thing about Azure that deserves to be taken into account is that it makes a distinction between the "stopped" and "deallocated" states of the virtual machine. You are billed when the virtual machine status is stopped, but not when the virtual machine is deallocated.

If you are operating from Azure Portal, pressing the Stop button will always deallocate the virtual machine. However, if you stop it through the operating system while you are connected, the virtual machine goes into the stopped mode, while in stopped mode, virtual machines will always be billed.

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