A virtual machine scale set is an Azure service that allows you to create and manage a group of identical virtual machines (VMs) that can automatically scale up or down based on demand or a set of rules. It simplifies the deployment and management of large-scale applications that need to handle varying amounts of traffic.
Here are some key features of virtual machine scale sets:
- Scaling Rules: You can define scaling rules to specify when the virtual machine scale set should scale up or down. These rules are based on a metric or a custom script that you define. You can use Azure Monitor to monitor metrics such as CPU utilization, network traffic, and memory usage. When the metric exceeds a certain threshold, the scale set can automatically add or remove VM instances. You can also use a custom script to define your own scaling rules. Azure provides a template to define custom scripts that can be used with virtual machine scale sets.
- Auto Scale: Virtual machine scale sets can automatically scale based on a predefined set of rules. This feature ensures that your application can handle the varying demands of traffic. You can specify minimum and maximum numbers of VMs that the scale set can have. When the demand is low, the scale set can reduce the number of VMs, and when the demand is high, the scale set can add more VMs.
- Rolling Upgrades: Virtual machine scale sets support rolling upgrades, which allow you to upgrade your application without downtime. You can update the VM instances in the scale set one by one, and the load balancer will automatically redirect traffic to the updated VM instances. This feature ensures that your application remains available during the upgrade process.
- Custom Images: You can use custom images to create VM instances in the scale set. Custom images can include pre-installed applications, operating system configurations, and security settings. You can use these images to quickly deploy your applications without the need to install and configure the applications on each VM instance.
- Load Balancing: Virtual machine scale sets are automatically load balanced across multiple VM instances. The Azure Load Balancer distributes traffic to the VM instances based on the rules that you define. The Load Balancer can also detect when a VM instance fails and automatically redirects traffic to a healthy VM instance.
- Regional Availability: Virtual machine scale sets are available in all Azure regions. You can deploy your application in the region closest to your users to minimize latency and improve performance.
- Azure Automation: You can use Azure Automation to automate common management tasks, such as scaling, patching, and backup. Azure Automation provides a set of runbooks that you can use to automate these tasks.
To create a virtual machine scale set, you need to define the following:
- Virtual machine image: You can use an Azure Marketplace image, a custom image, or a shared image gallery image to create VMs in the scale set.
- Virtual machine size: You can select the VM size based on your workload requirements.
- Scaling rules: You can define the scaling rules based on the metrics that you want to use for scaling.
- Network configuration: You need to define the virtual network and subnet configuration for the scale set.
- Storage account: You need to specify the storage account that you want to use for the VM instances in the scale set.
Steps to create a virtual machine scale set in Azure using the Azure Portal:
- Log in to the Azure Portal.
- Click on “+ Create a resource” in the left-hand menu and select “Virtual machine scale set.”
- Enter a name for your virtual machine scale set, choose the subscription, and select the resource group where you want to create the scale set.
- Select the operating system image you want to use, such as Windows or Linux.
- Choose the VM size and number of instances you want to create.
- Configure your network settings by choosing the virtual network and subnet where you want to deploy your VM instances.
- Define your load balancer settings, such as the load balancing algorithm and the health probe settings.
- Define your scaling rules by choosing the metrics you want to use for scaling, such as CPU utilization or memory usage.
- Set the minimum and maximum number of instances for your scale set.
- Review your settings and click on “Create” to create your virtual machine scale set.
Once your virtual machine scale set is created, you can manage it using the Azure Portal, Azure CLI, or Azure PowerShell. You can monitor the metrics, adjust the scaling rules, and perform other management tasks as needed.