Azure VM Scaling

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Scale Sets

Azure virtual machine scale sets let you create and manage a group of identical, load balanced VM instances. The number of machines can increase automatically, by hand or on a schedule.

• All VMs are created from the same OS image and provisioning configuration. In this way you can deploy hundreds of identical VMs.
• Scale sets support the use of Azure load balancer for basic layer-4 traffic distribution and Azure Application Gateway for advanced layer-7 traffic distribution and SSL termination.
• Scale sets are used to run multiple instances of a application. If one instance has a problem the other one will take over. The VMs can be spread over different Availability Zones.
• Machines in a scale set are placed over 5 fault domains and 5 update domains automatically.
• When the demand is higher you can use Autoscale based on different rules.
• Scale sets support up to 1000 VMs with normal images. With custom images the limit is 300 instances.

Autoscale

Automatically adjust the number of instances based on a set of rules. When the performance on one server is to high, Azure can scale up the capacity of the Scale set.

• Scale Out - If the application demand increases the load on the current instances, and the increased load is consistent. Autoscale can scale up the number of instances.
• Scale In - When the load is low for a long period of time. Autoscale can decrease the number of machines. The scale-in action reduces the cost.
• Scheduled event - Schedule events to automatically increase or decrease the capacity of your scale set at fixed times.

See the best practices for Autoscale.