Azure compute is an on-demand computing service for running cloud-based applications. It provides computing resources such as disks, processors, memory, networking, and operating systems. The resources are available on-demand and can typically be made available in minutes or even seconds. You pay only for the resources you use, and only for as long as you're using them.

Azure supports a wide range of computing solutions for development and testing, running applications, and extending your datacenter. The service supports Linux, Windows Server, SQL Server, Oracle, IBM, and SAP. Azure also has many services that can run virtual machines (VMs). Each service provides different options depending on your requirements. Some of the most prominent services are:

• Azure Virtual Machines
• Azure Container Instances
• Azure App Service
• Azure Functions (or serverless computing)

Virtual machines

Virtual machines are software emulations of physical computers. They include a virtual processor, memory, storage, and networking resources. VMs host an operating system, and you can install and run software just like a physical computer. When using a remote desktop client, you can use and control the VM as if you were sitting in front of it.

With Azure Virtual Machines, you can create and use VMs in the cloud. Virtual Machines provides infrastructure as a service (IaaS) and can be used in different ways. When you need total control over an operating system and environment, VMs are an ideal choice. Just like a physical computer, you can customize all the software running on the VM. This ability is helpful when you're running custom software or custom hosting configurations.

Virtual machine scale sets

Virtual machine scale sets are an Azure compute resource that you can use to deploy and manage a set of identical VMs. With all VMs configured the same, virtual machine scale sets are designed to support true autoscale. No pre-provisioning of VMs is required. For this reason, it's easier to build large-scale services targeting big compute, big data, and containerized workloads. As demand goes up, more VM instances can be added. As demand goes down, VM instances can be removed. The process can be manual, automated, or a combination of both.

Containers and Kubernetes

Container Instances and Azure Kubernetes Service are Azure compute resources that you can use to deploy and manage containers. Containers are lightweight, virtualized application environments. They're designed to be quickly created, scaled out, and stopped dynamically. You can run multiple instances of a containerized application on a single host machine.

App Service

With Azure App Service, you can quickly build, deploy, and scale enterprise-grade web, mobile, and API apps running on any platform. You can meet rigorous performance, scalability, security, and compliance requirements while using a fully managed platform to perform infrastructure maintenance. App Service is a platform as a service (PaaS) offering.

Functions

Functions are ideal when you're concerned only about the code running your service and not the underlying platform or infrastructure. They're commonly used when you need to perform work in response to an event (often via a REST request), timer, or message from another Azure service, and when that work can be completed quickly, within seconds or less.

Decide when to use Azure Virtual Machines

With Azure Virtual Machines, you can create and use VMs in the cloud. VMs provide infrastructure as a service (IaaS) in the form of a virtualized server and can be used in many ways. Just like a physical computer, you can customize all of the software running on the VM. VMs are an ideal choice when you need:

• Total control over the operating system (OS).
• The ability to run custom software.
• To use custom hosting configurations.

An Azure VM gives you the flexibility of virtualization without having to buy and maintain the physical hardware that runs the VM. You still need to configure, update, and maintain the software that runs on the VM.

You can create and provision a VM in minutes when you select a preconfigured VM image. Selecting an image is one of the most important decisions you'll make when you create a VM. An image is a template used to create a VM. These templates already include an OS and often other software, like development tools or web hosting environments.

Examples of when to use VMs

• During testing and development. VMs provide a quick and easy way to create different OS and application configurations. Test and development personnel can then easily delete the VMs when they no longer need them.

• When running applications in the cloud. The ability to run certain applications in the public cloud as opposed to creating a traditional infrastructure to run them can provide substantial economic benefits. For example, an application might need to handle fluctuations in demand. Shutting down VMs when you don't need them or quickly starting them up to meet a sudden increase in demand means you pay only for the resources you use.

• When extending your datacenter to the cloud. An organization can extend the capabilities of its own on-premises network by creating a virtual network in Azure and adding VMs to that virtual network. Applications like SharePoint can then run on an Azure VM instead of running locally. This arrangement makes it easier or less expensive to deploy than in an on-premises environment.

• During disaster recovery. As with running certain types of applications in the cloud and extending an on-premises network to the cloud, you can get significant cost savings by using an IaaS-based approach to disaster recovery. If a primary datacenter fails, you can create VMs running on Azure to run your critical applications and then shut them down when the primary datacenter becomes operational again.

Move to the cloud with VMs

VMs are also an excellent choice when you move from a physical server to the cloud (also known as lift and shift). You can create an image of the physical server and host it within a VM with little or no changes. Just like a physical on-premises server, you must maintain the VM. You update the installed OS and the software it runs.

Scale VMs in Azure

You can run single VMs for testing, development, or minor tasks. Or you can group VMs together to provide high availability, scalability, and redundancy. No matter what your uptime requirements are, Azure has several features that can meet them. These features include:

• Virtual machine scale sets
• Azure Batch

What are virtual machine scale sets?

Virtual machine scale sets let you create and manage a group of identical, load-balanced VMs. Imagine you're running a website that enables scientists to upload astronomy images that need to be processed. If you duplicated the VM, you'd normally need to configure an additional service to route requests between multiple instances of the website. Virtual machine scale sets could do that work for you.

Scale sets allow you to centrally manage, configure, and update a large number of VMs in minutes to provide highly available applications. The number of VM instances can automatically increase or decrease in response to demand or a defined schedule. With virtual machine scale sets, you can build large-scale services for areas such as compute, big data, and container workloads.

What is Azure Batch?

Azure Batch enables large-scale parallel and high-performance computing (HPC) batch jobs with the ability to scale to tens, hundreds, or thousands of VMs.

When you're ready to run a job, Batch does the following:

• Starts a pool of compute VMs for you.
• Installs applications and staging data.
• Runs jobs with as many tasks as you have.
• Identifies failures.
• Requeues work.
• Scales down the pool as work completes.

There might be situations in which you need raw computing power or supercomputer-level compute power. Azure provides these capabilities.