More clarity on difference between VM and VM instances and Availability Sets (AS)

Question

Hello everyone,

On the internet, I saw the difference in the image above- between a VM and a VM instance.

So, I infer from this that VMs have different OS systems and all of them operate independently.

But VM instances are templates or blueprints of a VM, that can be spun or downsized as needed. They also run independently but based on the same initial config that they got from the template.

==> Obviously VM instances are much faster than VMs because they are based on configs and don't need an OS or CPU and other resources unlike VMs. Please correct the above. Am I right?

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Also, are Availability Sets are specifically designed to handle VM instances?

So, when you deploy VMs into an availability set, Azure distributes the VMs across multiple physical servers, network switches, and power sources within a data center:

Does it mean deployment of VM instances across multiple physical servers....because based on the difference above, it would be time consuming for VMs to be deployed quickly across multiple servers? And as mentioned in the module, we are paying for VM instances that we create (obviously, using Azure portal or CLI etc.)

Kindly, please clarify,

Thank you

Marouf

Answer 1

Hi Marouf Ali,

Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.

Here is the detailed information about your query.

You are partially correct regarding VM and VM Instance. VM instances are templates or blueprints of a VM, that can be spun or downsized as needed but VM instances still require an operating system (OS), CPU, memory, storage, and other resources just like traditional virtual machines (VMs). The main distinction isn’t that they lack these resources but rather how they’re created and deployed.

Please refer to below document for more information https://learn.microsoft.com/en-us/azure/virtual-machines/overview

Yes, Availability Sets in Azure are specifically designed to enhance the availability and reliability of virtual machines (VMs), including VM instances. When you deploy virtual machines (VMs) within an Availability Set in Azure, the platform distributes them across various physical servers, network switches, and power supplies within a data center. This setup ensures that a failure in one physical component, such as a server or power source, will not impact all VMs within the set, enhancing your application's reliability and uptime. The ability to deploy VMs swiftly across multiple servers is a core benefit of cloud infrastructure. Azure takes care of the distribution process, placing each VM across different servers and network components to bolster fault tolerance and service continuity.

Although deploying VMs across multiple servers might seem time-intensive, Azure’s infrastructure is optimized for rapid provisioning, often enabling VM deployment within minutes, which allows for swift scaling as demand fluctuates. Billing is based on the number of VMs running, regardless of deployment speed, so costs depend on the quantity of active instances rather than the time it takes to deploy them.

Please refer to this for detailed information on Availability sets https://learn.microsoft.com/en-us/azure/virtual-machines/availability-set-overview

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